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	$32.30	7.870%	$34.842	$34.84	$34.85	$34.80
Purchase #2	$156.61	5.625%	$165.4193	$165.42	$165.40	$165.40
Purchase #3	$82.57	7.548%	$88.8024	$88.80	$88.80	$88.80
Purchase #4	$243.55	5.367%	$256.6213	$256.62	$256.60	$256.60
Purchase #5	$175.69	13.505%	$199.4169	$199.42	$199.40	$199.40
Purchase #6	$210.50	13.381%	$238.667	$238.67	$238.65	$238.70
Purchase #7	$156.67	7.819%	$168.92	$168.92	$168.90	$168.90
7 purchase totals =	$1,057.89		$1,152.6889	$1,152.69	$1,152.60	$1,152.60