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	$58.86	5.621%	$62.1685	$62.17	$62.15	$62.20
Purchase #2	$29.91	8.380%	$32.4165	$32.42	$32.40	$32.40
Purchase #3	$219.38	13.222%	$248.3864	$248.39	$248.40	$248.40
Purchase #4	$79.92	6.870%	$85.4105	$85.41	$85.40	$85.40
Purchase #5	$21.48	3.716%	$22.2782	$22.28	$22.30	$22.30
Purchase #6	$127.91	5.469%	$134.9054	$134.91	$134.90	$134.90
Purchase #7	$247.78	11.372%	$275.9575	$275.96	$275.95	$276.00
7 purchase totals =	$785.24		$861.5230	$861.54	$861.50	$861.60