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	$118.44	7.298%	$127.0838	$127.08	$127.10	$127.10
Purchase #2	$110.58	11.543%	$123.3442	$123.34	$123.35	$123.30
Purchase #3	$24.89	4.861%	$26.0999	$26.10	$26.10	$26.10
Purchase #4	$238.99	3.718%	$247.8756	$247.88	$247.90	$247.90
Purchase #5	$209.46	8.583%	$227.438	$227.44	$227.45	$227.40
Purchase #6	$55.68	7.620%	$59.9228	$59.92	$59.90	$59.90
Purchase #7	$127.95	10.252%	$141.0674	$141.07	$141.05	$141.10
7 purchase totals =	$885.99		$952.8317	$952.83	$952.85	$952.80