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	$50.75	3.696%	$52.6257	$52.63	$52.65	$52.60
Purchase #2	$86.58	4.632%	$90.5904	$90.59	$90.60	$90.60
Purchase #3	$84.54	12.244%	$94.8911	$94.89	$94.90	$94.90
Purchase #4	$210.69	9.324%	$230.3347	$230.33	$230.35	$230.30
Purchase #5	$119.82	9.421%	$131.1082	$131.11	$131.10	$131.10
Purchase #6	$199.84	8.512%	$216.8504	$216.85	$216.85	$216.90
Purchase #7	$54.61	3.733%	$56.6486	$56.65	$56.65	$56.60
7 purchase totals =	$806.83		$873.0491	$873.05	$873.10	$873.00