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	$236.46	11.693%	$264.1093	$264.11	$264.10	$264.10
Purchase #2	$153.81	10.466%	$169.9078	$169.91	$169.90	$169.90
Purchase #3	$157.48	13.841%	$179.2768	$179.28	$179.30	$179.30
Purchase #4	$71.53	13.420%	$81.1293	$81.13	$81.15	$81.10
Purchase #5	$18.96	13.507%	$21.5209	$21.52	$21.50	$21.50
Purchase #6	$137.67	6.516%	$146.6406	$146.64	$146.65	$146.60
Purchase #7	$165.75	11.136%	$184.2079	$184.21	$184.20	$184.20
7 purchase totals =	$941.66		$1,046.7926	$1,046.80	$1,046.80	$1,046.70