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	$140.89	4.362%	$147.0356	$147.04	$147.05	$147.00
Purchase #2	$243.58	9.573%	$266.8979	$266.90	$266.90	$266.90
Purchase #3	$55.31	10.729%	$61.2442	$61.24	$61.25	$61.20
Purchase #4	$192.63	7.244%	$206.5841	$206.58	$206.60	$206.60
Purchase #5	$153.74	7.661%	$165.518	$165.52	$165.50	$165.50
Purchase #6	$127.40	9.488%	$139.4877	$139.49	$139.50	$139.50
Purchase #7	$123.97	10.788%	$137.3439	$137.34	$137.35	$137.30
7 purchase totals =	$1,037.52		$1,124.1114	$1,124.11	$1,124.15	$1,124.00