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	$92.79	9.525%	$101.6282	$101.63	$101.65	$101.60
Purchase #2	$235.31	13.261%	$266.5145	$266.51	$266.50	$266.50
Purchase #3	$67.63	7.244%	$72.5291	$72.53	$72.55	$72.50
Purchase #4	$158.25	4.370%	$165.1655	$165.17	$165.15	$165.20
Purchase #5	$243.62	7.680%	$262.33	$262.33	$262.35	$262.30
Purchase #6	$33.87	9.301%	$37.0202	$37.02	$37.00	$37.00
Purchase #7	$17.85	9.130%	$19.4797	$19.48	$19.50	$19.50
7 purchase totals =	$849.32		$924.6672	$924.67	$924.70	$924.60