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	$95.31	10.281%	$105.1088	$105.11	$105.10	$105.10
Purchase #2	$71.69	10.418%	$79.1587	$79.16	$79.15	$79.20
Purchase #3	$44.97	9.290%	$49.1477	$49.15	$49.15	$49.10
Purchase #4	$70.85	11.133%	$78.7377	$78.74	$78.75	$78.70
Purchase #5	$189.27	9.280%	$206.8343	$206.83	$206.85	$206.80
Purchase #6	$157.74	11.269%	$175.5157	$175.52	$175.50	$175.50
Purchase #7	$132.90	6.803%	$141.9412	$141.94	$141.95	$141.90
7 purchase totals =	$762.73		$836.4441	$836.45	$836.45	$836.30