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	$59.95	13.617%	$68.1134	$68.11	$68.10	$68.10
Purchase #2	$114.46	6.700%	$122.1288	$122.13	$122.15	$122.10
Purchase #3	$66.29	8.273%	$71.7742	$71.77	$71.75	$71.80
Purchase #4	$34.85	7.870%	$37.5927	$37.59	$37.60	$37.60
Purchase #5	$240.73	9.496%	$263.5897	$263.59	$263.60	$263.60
Purchase #6	$165.57	8.193%	$179.1352	$179.14	$179.15	$179.10
Purchase #7	$45.34	11.585%	$50.5926	$50.59	$50.60	$50.60
7 purchase totals =	$727.19		$792.9266	$792.92	$792.95	$792.90