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	$193.86	12.132%	$217.3791	$217.38	$217.40	$217.40
Purchase #2	$67.98	9.467%	$74.4157	$74.42	$74.40	$74.40
Purchase #3	$196.80	9.762%	$216.0116	$216.01	$216.00	$216.00
Purchase #4	$209.45	6.389%	$222.8318	$222.83	$222.85	$222.80
Purchase #5	$64.89	11.129%	$72.1116	$72.11	$72.10	$72.10
Purchase #6	$92.28	10.718%	$102.1706	$102.17	$102.15	$102.20
Purchase #7	$32.75	11.509%	$36.5192	$36.52	$36.50	$36.50
7 purchase totals =	$858.01		$941.4396	$941.44	$941.40	$941.40