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	$53.44	11.571%	$59.6235	$59.62	$59.60	$59.60
Purchase #2	$234.48	5.354%	$247.0341	$247.03	$247.05	$247.00
Purchase #3	$60.35	8.428%	$65.4363	$65.44	$65.45	$65.40
Purchase #4	$35.43	5.317%	$37.3138	$37.31	$37.30	$37.30
Purchase #5	$95.72	13.809%	$108.938	$108.94	$108.95	$108.90
Purchase #6	$81.58	11.832%	$91.2325	$91.23	$91.25	$91.20
Purchase #7	$136.30	7.581%	$146.6329	$146.63	$146.65	$146.60
7 purchase totals =	$697.30		$756.2111	$756.20	$756.25	$756.00