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	$159.86	3.448%	$165.372	$165.37	$165.35	$165.40
Purchase #2	$214.91	4.222%	$223.9835	$223.98	$224.00	$224.00
Purchase #3	$34.89	6.637%	$37.2056	$37.21	$37.20	$37.20
Purchase #4	$223.28	12.676%	$251.583	$251.58	$251.60	$251.60
Purchase #5	$83.61	8.203%	$90.4685	$90.47	$90.45	$90.50
Purchase #6	$151.58	8.539%	$164.5234	$164.52	$164.50	$164.50
Purchase #7	$189.88	9.810%	$208.5072	$208.51	$208.50	$208.50
7 purchase totals =	$1,058.01		$1,141.6432	$1,141.64	$1,141.60	$1,141.70