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	$87.64	7.724%	$94.4093	$94.41	$94.40	$94.40
Purchase #2	$33.88	13.377%	$38.4121	$38.41	$38.40	$38.40
Purchase #3	$33.50	5.850%	$35.4598	$35.46	$35.45	$35.50
Purchase #4	$94.30	5.760%	$99.7317	$99.73	$99.75	$99.70
Purchase #5	$31.69	3.699%	$32.8622	$32.86	$32.85	$32.90
Purchase #6	$145.59	9.714%	$159.7326	$159.73	$159.75	$159.70
Purchase #7	$7.50	8.154%	$8.1116	$8.11	$8.10	$8.10
7 purchase totals =	$434.10		$468.7193	$468.71	$468.70	$468.70