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	$213.86	4.573%	$223.6398	$223.64	$223.65	$223.60
Purchase #2	$89.70	12.872%	$101.2462	$101.25	$101.25	$101.20
Purchase #3	$134.79	5.310%	$141.9473	$141.95	$141.95	$141.90
Purchase #4	$197.47	12.485%	$222.1241	$222.12	$222.10	$222.10
Purchase #5	$34.55	5.490%	$36.4468	$36.45	$36.45	$36.40
Purchase #6	$211.85	8.404%	$229.6539	$229.65	$229.65	$229.70
Purchase #7	$203.43	13.781%	$231.4647	$231.46	$231.45	$231.50
7 purchase totals =	$1,085.65		$1,186.5228	$1,186.52	$1,186.50	$1,186.40