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	$243.63	13.472%	$276.4518	$276.45	$276.45	$276.50
Purchase #2	$124.96	9.298%	$136.5788	$136.58	$136.60	$136.60
Purchase #3	$147.31	13.580%	$167.3147	$167.31	$167.30	$167.30
Purchase #4	$232.61	11.589%	$259.5672	$259.57	$259.55	$259.60
Purchase #5	$191.45	4.707%	$200.4616	$200.46	$200.45	$200.50
Purchase #6	$234.85	3.668%	$243.4643	$243.46	$243.45	$243.50
Purchase #7	$222.38	7.201%	$238.3936	$238.39	$238.40	$238.40
7 purchase totals =	$1,397.19		$1,522.2320	$1,522.22	$1,522.20	$1,522.40