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	$84.98	13.300%	$96.2823	$96.28	$96.30	$96.30
Purchase #2	$40.50	12.375%	$45.5119	$45.51	$45.50	$45.50
Purchase #3	$61.95	10.230%	$68.2875	$68.29	$68.30	$68.30
Purchase #4	$198.81	7.626%	$213.9713	$213.97	$213.95	$214.00
Purchase #5	$175.65	11.367%	$195.6161	$195.62	$195.60	$195.60
Purchase #6	$105.94	3.460%	$109.6055	$109.61	$109.60	$109.60
Purchase #7	$87.47	3.594%	$90.6137	$90.61	$90.60	$90.60
7 purchase totals =	$755.30		$819.8883	$819.89	$819.85	$819.90