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	$37.33	11.685%	$41.692	$41.69	$41.70	$41.70
Purchase #2	$106.34	5.428%	$112.1121	$112.11	$112.10	$112.10
Purchase #3	$17.62	10.634%	$19.4937	$19.49	$19.50	$19.50
Purchase #4	$95.92	12.148%	$107.5724	$107.57	$107.55	$107.60
Purchase #5	$176.42	11.177%	$196.1385	$196.14	$196.15	$196.10
Purchase #6	$154.86	10.599%	$171.2736	$171.27	$171.25	$171.30
Purchase #7	$141.72	10.144%	$156.0961	$156.10	$156.10	$156.10
7 purchase totals =	$730.21		$804.3784	$804.37	$804.35	$804.40