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	$59.35	13.372%	$67.2863	$67.29	$67.30	$67.30
Purchase #2	$121.38	12.329%	$136.3449	$136.34	$136.35	$136.30
Purchase #3	$219.86	3.595%	$227.764	$227.76	$227.75	$227.80
Purchase #4	$125.25	4.316%	$130.6558	$130.66	$130.65	$130.70
Purchase #5	$139.90	4.440%	$146.1116	$146.11	$146.10	$146.10
Purchase #6	$170.32	4.545%	$178.061	$178.06	$178.05	$178.10
Purchase #7	$65.51	9.732%	$71.8854	$71.89	$71.90	$71.90
7 purchase totals =	$901.57		$958.1090	$958.11	$958.10	$958.20