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	$42.82	9.513%	$46.8935	$46.89	$46.90	$46.90
Purchase #2	$244.77	8.591%	$265.7982	$265.80	$265.80	$265.80
Purchase #3	$88.36	12.622%	$99.5128	$99.51	$99.50	$99.50
Purchase #4	$158.60	11.269%	$176.4726	$176.47	$176.45	$176.50
Purchase #5	$208.97	11.581%	$233.1708	$233.17	$233.15	$233.20
Purchase #6	$227.35	11.674%	$253.8908	$253.89	$253.90	$253.90
Purchase #7	$82.61	10.619%	$91.3824	$91.38	$91.40	$91.40
7 purchase totals =	$1,053.48		$1,167.1211	$1,167.11	$1,167.10	$1,167.20