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	$231.26	13.672%	$262.8779	$262.88	$262.90	$262.90
Purchase #2	$141.72	9.651%	$155.3974	$155.40	$155.40	$155.40
Purchase #3	$82.92	3.409%	$85.7467	$85.75	$85.75	$85.70
Purchase #4	$174.57	12.485%	$196.3651	$196.37	$196.35	$196.40
Purchase #5	$250.43	8.341%	$271.3184	$271.32	$271.30	$271.30
Purchase #6	$135.31	13.467%	$153.5322	$153.53	$153.55	$153.50
Purchase #7	$110.98	6.547%	$118.2459	$118.25	$118.25	$118.20
7 purchase totals =	$1,127.19		$1,243.4836	$1,243.50	$1,243.50	$1,243.40