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	$137.68	9.409%	$150.6343	$150.63	$150.65	$150.60
Purchase #2	$74.38	11.218%	$82.7239	$82.72	$82.70	$82.70
Purchase #3	$42.91	4.345%	$44.7744	$44.77	$44.75	$44.80
Purchase #4	$211.92	8.477%	$229.8845	$229.88	$229.90	$229.90
Purchase #5	$91.71	13.565%	$104.1505	$104.15	$104.15	$104.20
Purchase #6	$132.52	5.589%	$139.9265	$139.93	$139.95	$139.90
Purchase #7	$159.90	10.500%	$176.6895	$176.69	$176.70	$176.70
7 purchase totals =	$851.02		$928.7836	$928.77	$928.80	$928.80