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	$246.86	11.119%	$274.3084	$274.31	$274.30	$274.30
Purchase #2	$150.70	5.603%	$159.1437	$159.14	$159.15	$159.10
Purchase #3	$41.26	13.227%	$46.7175	$46.72	$46.70	$46.70
Purchase #4	$166.70	10.872%	$184.8236	$184.82	$184.80	$184.80
Purchase #5	$114.42	5.110%	$120.2669	$120.27	$120.25	$120.30
Purchase #6	$196.83	5.424%	$207.5061	$207.51	$207.50	$207.50
Purchase #7	$68.48	5.541%	$72.2745	$72.27	$72.25	$72.30
7 purchase totals =	$985.25		$1,065.0407	$1,065.04	$1,064.95	$1,065.00