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	$76.85	11.487%	$85.6778	$85.68	$85.70	$85.70
Purchase #2	$221.33	12.669%	$249.3703	$249.37	$249.35	$249.40
Purchase #3	$171.70	11.778%	$191.9228	$191.92	$191.90	$191.90
Purchase #4	$88.52	12.200%	$99.3194	$99.32	$99.30	$99.30
Purchase #5	$222.29	11.601%	$248.0779	$248.08	$248.10	$248.10
Purchase #6	$214.93	9.104%	$234.4972	$234.50	$234.50	$234.50
Purchase #7	$212.89	8.734%	$231.4838	$231.48	$231.50	$231.50
7 purchase totals =	$1,208.51		$1,340.3492	$1,340.35	$1,340.35	$1,340.40