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	$158.33	6.251%	$168.2272	$168.23	$168.25	$168.20
Purchase #2	$33.53	10.621%	$37.0912	$37.09	$37.10	$37.10
Purchase #3	$69.71	13.546%	$79.1529	$79.15	$79.15	$79.20
Purchase #4	$57.90	11.722%	$64.687	$64.69	$64.70	$64.70
Purchase #5	$110.38	4.264%	$115.0866	$115.09	$115.10	$115.10
Purchase #6	$165.57	3.612%	$171.5504	$171.55	$171.55	$171.60
Purchase #7	$106.67	4.162%	$111.1096	$111.11	$111.10	$111.10
7 purchase totals =	$702.09		$746.9049	$746.91	$746.95	$747.00