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	$245.93	6.493%	$261.8982	$261.90	$261.90	$261.90
Purchase #2	$223.82	13.278%	$253.5388	$253.54	$253.55	$253.50
Purchase #3	$233.98	11.449%	$260.7684	$260.77	$260.75	$260.80
Purchase #4	$39.40	3.436%	$40.7538	$40.75	$40.75	$40.80
Purchase #5	$145.26	13.813%	$165.3248	$165.32	$165.30	$165.30
Purchase #6	$139.79	11.177%	$155.4143	$155.41	$155.40	$155.40
Purchase #7	$32.35	7.742%	$34.8545	$34.85	$34.85	$34.90
7 purchase totals =	$1,060.53		$1,172.5528	$1,172.54	$1,172.50	$1,172.60