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	$67.60	13.406%	$76.6625	$76.66	$76.65	$76.70
Purchase #2	$140.77	11.464%	$156.9079	$156.91	$156.90	$156.90
Purchase #3	$38.63	11.785%	$43.1825	$43.18	$43.20	$43.20
Purchase #4	$76.56	7.619%	$82.3931	$82.39	$82.40	$82.40
Purchase #5	$29.33	7.145%	$31.4256	$31.43	$31.45	$31.40
Purchase #6	$52.50	10.466%	$57.9947	$57.99	$58.00	$58.00
Purchase #7	$169.28	7.742%	$182.3857	$182.39	$182.40	$182.40
7 purchase totals =	$574.67		$630.9520	$630.95	$631.00	$631.00