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	$235.46	12.227%	$264.2497	$264.25	$264.25	$264.20
Purchase #2	$222.32	13.186%	$251.6351	$251.64	$251.65	$251.60
Purchase #3	$211.70	7.853%	$228.3248	$228.32	$228.30	$228.30
Purchase #4	$123.90	11.755%	$138.4644	$138.46	$138.45	$138.50
Purchase #5	$6.43	8.538%	$6.979	$6.98	$7.00	$7.00
Purchase #6	$72.31	13.633%	$82.168	$82.17	$82.15	$82.20
Purchase #7	$76.61	8.426%	$83.0652	$83.07	$83.05	$83.10
7 purchase totals =	$948.73		$1,054.8862	$1,054.89	$1,054.85	$1,054.90