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	$154.71	12.356%	$173.826	$173.83	$173.85	$173.80
Purchase #2	$76.55	12.733%	$86.2971	$86.30	$86.30	$86.30
Purchase #3	$152.63	12.702%	$172.0171	$172.02	$172.00	$172.00
Purchase #4	$57.56	13.468%	$65.3122	$65.31	$65.30	$65.30
Purchase #5	$63.90	13.301%	$72.3993	$72.40	$72.40	$72.40
Purchase #6	$116.77	10.308%	$128.8067	$128.81	$128.80	$128.80
Purchase #7	$147.83	6.281%	$157.1152	$157.12	$157.10	$157.10
7 purchase totals =	$769.95		$855.7736	$855.79	$855.75	$855.70