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	$177.99	10.516%	$196.7074	$196.71	$196.70	$196.70
Purchase #2	$136.25	8.749%	$148.1705	$148.17	$148.15	$148.20
Purchase #3	$128.98	13.707%	$146.6593	$146.66	$146.65	$146.70
Purchase #4	$95.79	9.811%	$105.188	$105.19	$105.20	$105.20
Purchase #5	$250.71	4.630%	$262.3179	$262.32	$262.30	$262.30
Purchase #6	$40.61	11.364%	$45.2249	$45.22	$45.20	$45.20
Purchase #7	$41.92	4.258%	$43.705	$43.71	$43.70	$43.70
7 purchase totals =	$872.25		$947.9730	$947.98	$947.90	$948.00