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	$113.67	8.770%	$123.6389	$123.64	$123.65	$123.60
Purchase #2	$154.58	9.173%	$168.7596	$168.76	$168.75	$168.80
Purchase #3	$139.79	13.594%	$158.7931	$158.79	$158.80	$158.80
Purchase #4	$164.48	6.351%	$174.9261	$174.93	$174.95	$174.90
Purchase #5	$164.90	10.747%	$182.6218	$182.62	$182.60	$182.60
Purchase #6	$65.49	10.344%	$72.2643	$72.26	$72.25	$72.30
Purchase #7	$31.68	7.723%	$34.1266	$34.13	$34.15	$34.10
7 purchase totals =	$834.59		$915.1304	$915.13	$915.15	$915.10