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	$210.77	13.153%	$238.4926	$238.49	$238.50	$238.50
Purchase #2	$75.78	11.419%	$84.4333	$84.43	$84.45	$84.40
Purchase #3	$124.95	11.855%	$139.7628	$139.76	$139.75	$139.80
Purchase #4	$218.76	13.622%	$248.5595	$248.56	$248.55	$248.60
Purchase #5	$147.38	13.661%	$167.5136	$167.51	$167.50	$167.50
Purchase #6	$43.41	5.820%	$45.9365	$45.94	$45.95	$45.90
Purchase #7	$199.82	8.222%	$216.2492	$216.25	$216.25	$216.20
7 purchase totals =	$1,020.87		$1,140.9475	$1,140.94	$1,140.95	$1,140.90