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	$198.31	10.457%	$219.0473	$219.05	$219.05	$219.00
Purchase #2	$69.60	11.581%	$77.6604	$77.66	$77.65	$77.70
Purchase #3	$37.77	12.104%	$42.3417	$42.34	$42.35	$42.30
Purchase #4	$208.85	11.783%	$233.4588	$233.46	$233.45	$233.50
Purchase #5	$100.58	11.218%	$111.8631	$111.86	$111.85	$111.90
Purchase #6	$237.56	9.502%	$260.133	$260.13	$260.15	$260.10
Purchase #7	$157.97	12.831%	$178.2391	$178.24	$178.25	$178.20
7 purchase totals =	$1,010.64		$1,122.7434	$1,122.74	$1,122.75	$1,122.70