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	$219.28	13.291%	$248.4245	$248.42	$248.40	$248.40
Purchase #2	$214.67	13.625%	$243.9188	$243.92	$243.90	$243.90
Purchase #3	$100.98	12.201%	$113.3006	$113.30	$113.30	$113.30
Purchase #4	$156.60	5.390%	$165.0407	$165.04	$165.05	$165.00
Purchase #5	$52.73	8.648%	$57.2901	$57.29	$57.30	$57.30
Purchase #6	$185.41	3.507%	$191.9123	$191.91	$191.90	$191.90
Purchase #7	$39.96	8.293%	$43.2739	$43.27	$43.25	$43.30
7 purchase totals =	$969.63		$1,063.1609	$1,063.15	$1,063.10	$1,063.10