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	$214.42	5.311%	$225.8078	$225.81	$225.80	$225.80
Purchase #2	$175.53	11.849%	$196.3285	$196.33	$196.35	$196.30
Purchase #3	$24.71	13.780%	$28.115	$28.12	$28.10	$28.10
Purchase #4	$156.38	6.201%	$166.0771	$166.08	$166.10	$166.10
Purchase #5	$90.73	6.724%	$96.8307	$96.83	$96.85	$96.80
Purchase #6	$247.59	6.215%	$262.9777	$262.98	$263.00	$263.00
Purchase #7	$25.74	13.231%	$29.1457	$29.15	$29.15	$29.10
7 purchase totals =	$935.10		$1,005.2825	$1,005.30	$1,005.35	$1,005.20