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	$238.46	4.731%	$249.7415	$249.74	$249.75	$249.70
Purchase #2	$195.29	7.761%	$210.4465	$210.45	$210.45	$210.40
Purchase #3	$228.81	12.260%	$256.8621	$256.86	$256.85	$256.90
Purchase #4	$31.36	9.776%	$34.4258	$34.43	$34.45	$34.40
Purchase #5	$42.83	8.549%	$46.4915	$46.49	$46.50	$46.50
Purchase #6	$175.78	13.500%	$199.5103	$199.51	$199.50	$199.50
Purchase #7	$147.25	5.467%	$155.3002	$155.30	$155.30	$155.30
7 purchase totals =	$1,059.78		$1,152.7779	$1,152.78	$1,152.80	$1,152.70