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	$154.54	8.856%	$168.2261	$168.23	$168.25	$168.20
Purchase #2	$64.43	10.390%	$71.1243	$71.12	$71.10	$71.10
Purchase #3	$159.63	6.306%	$169.6963	$169.70	$169.70	$169.70
Purchase #4	$78.73	5.559%	$83.1066	$83.11	$83.10	$83.10
Purchase #5	$121.42	5.362%	$127.9305	$127.93	$127.95	$127.90
Purchase #6	$71.35	10.601%	$78.9138	$78.91	$78.90	$78.90
Purchase #7	$20.98	10.490%	$23.1808	$23.18	$23.20	$23.20
7 purchase totals =	$671.08		$722.1784	$722.18	$722.20	$722.10