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	$227.47	9.141%	$248.263	$248.26	$248.25	$248.30
Purchase #2	$53.38	3.517%	$55.2574	$55.26	$55.25	$55.30
Purchase #3	$35.42	4.246%	$36.9239	$36.92	$36.90	$36.90
Purchase #4	$98.68	10.503%	$109.0444	$109.04	$109.05	$109.00
Purchase #5	$75.29	4.687%	$78.8188	$78.82	$78.80	$78.80
Purchase #6	$33.55	12.711%	$37.8145	$37.81	$37.80	$37.80
Purchase #7	$53.73	13.733%	$61.1087	$61.11	$61.10	$61.10
7 purchase totals =	$577.52		$627.2307	$627.22	$627.15	$627.20