Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$161.41	12.670%	$181.8606	$181.86	$181.85	$181.90
Purchase #2	$173.32	4.390%	$180.9287	$180.93	$180.95	$180.90
Purchase #3	$78.84	8.200%	$85.3049	$85.30	$85.30	$85.30
Purchase #4	$127.35	5.405%	$134.2333	$134.23	$134.25	$134.20
Purchase #5	$121.52	7.354%	$130.4566	$130.46	$130.45	$130.50
Purchase #6	$109.61	12.852%	$123.6971	$123.70	$123.70	$123.70
Purchase #7	$142.31	5.847%	$150.6309	$150.63	$150.65	$150.60
7 purchase totals =	$914.36		$987.1121	$987.11	$987.15	$987.10