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	$59.44	10.499%	$65.6806	$65.68	$65.70	$65.70
Purchase #2	$225.76	13.626%	$256.5221	$256.52	$256.50	$256.50
Purchase #3	$229.39	13.762%	$260.9587	$260.96	$260.95	$261.00
Purchase #4	$13.37	11.175%	$14.8641	$14.86	$14.85	$14.90
Purchase #5	$207.53	10.549%	$229.4223	$229.42	$229.40	$229.40
Purchase #6	$67.66	8.820%	$73.6276	$73.63	$73.65	$73.60
Purchase #7	$199.86	11.165%	$222.1744	$222.17	$222.15	$222.20
7 purchase totals =	$1,003.01		$1,123.2498	$1,123.24	$1,123.20	$1,123.30