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	$183.69	8.854%	$199.9539	$199.95	$199.95	$200.00
Purchase #2	$200.74	8.784%	$218.373	$218.37	$218.35	$218.40
Purchase #3	$51.84	6.667%	$55.2962	$55.30	$55.30	$55.30
Purchase #4	$78.66	13.417%	$89.2138	$89.21	$89.20	$89.20
Purchase #5	$53.83	13.657%	$61.1816	$61.18	$61.20	$61.20
Purchase #6	$34.67	13.442%	$39.3303	$39.33	$39.35	$39.30
Purchase #7	$108.91	4.805%	$114.1431	$114.14	$114.15	$114.10
7 purchase totals =	$712.34		$777.4919	$777.48	$777.50	$777.50