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	$142.47	12.813%	$160.7247	$160.72	$160.70	$160.70
Purchase #2	$35.31	12.430%	$39.699	$39.70	$39.70	$39.70
Purchase #3	$124.96	9.132%	$136.3713	$136.37	$136.35	$136.40
Purchase #4	$93.53	9.506%	$102.421	$102.42	$102.40	$102.40
Purchase #5	$40.90	4.705%	$42.8243	$42.82	$42.80	$42.80
Purchase #6	$228.83	11.362%	$254.8297	$254.83	$254.85	$254.80
Purchase #7	$41.51	13.823%	$47.2479	$47.25	$47.25	$47.20
7 purchase totals =	$707.51		$784.1179	$784.11	$784.05	$784.00