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	$190.40	10.374%	$210.1521	$210.15	$210.15	$210.20
Purchase #2	$203.51	5.266%	$214.2268	$214.23	$214.25	$214.20
Purchase #3	$171.40	8.446%	$185.8764	$185.88	$185.90	$185.90
Purchase #4	$60.72	11.797%	$67.8831	$67.88	$67.90	$67.90
Purchase #5	$247.95	12.232%	$278.2792	$278.28	$278.30	$278.30
Purchase #6	$19.80	5.536%	$20.8961	$20.90	$20.90	$20.90
Purchase #7	$214.50	6.262%	$227.932	$227.93	$227.95	$227.90
7 purchase totals =	$1,108.28		$1,205.2457	$1,205.25	$1,205.35	$1,205.30