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	$98.49	10.320%	$108.6542	$108.65	$108.65	$108.70
Purchase #2	$33.97	10.278%	$37.4614	$37.46	$37.45	$37.50
Purchase #3	$193.82	8.399%	$210.0989	$210.10	$210.10	$210.10
Purchase #4	$61.50	10.351%	$67.8659	$67.87	$67.85	$67.90
Purchase #5	$190.89	9.454%	$208.9367	$208.94	$208.95	$208.90
Purchase #6	$111.59	11.222%	$124.1126	$124.11	$124.10	$124.10
Purchase #7	$146.80	4.320%	$153.1418	$153.14	$153.15	$153.10
7 purchase totals =	$837.06		$910.2715	$910.27	$910.25	$910.30