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	$91.31	3.665%	$94.6565	$94.66	$94.65	$94.70
Purchase #2	$99.68	12.201%	$111.842	$111.84	$111.85	$111.80
Purchase #3	$44.86	13.800%	$51.0507	$51.05	$51.05	$51.10
Purchase #4	$92.58	4.345%	$96.6026	$96.60	$96.60	$96.60
Purchase #5	$38.29	7.357%	$41.107	$41.11	$41.10	$41.10
Purchase #6	$90.76	4.246%	$94.6137	$94.61	$94.60	$94.60
Purchase #7	$175.84	5.472%	$185.462	$185.46	$185.45	$185.50
7 purchase totals =	$633.32		$675.3345	$675.33	$675.30	$675.40