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	$220.75	10.737%	$244.4519	$244.45	$244.45	$244.50
Purchase #2	$249.51	7.279%	$267.6718	$267.67	$267.65	$267.70
Purchase #3	$90.26	13.362%	$102.3205	$102.32	$102.30	$102.30
Purchase #4	$132.25	8.709%	$143.7677	$143.77	$143.75	$143.80
Purchase #5	$164.45	7.302%	$176.4581	$176.46	$176.45	$176.50
Purchase #6	$42.57	6.592%	$45.3762	$45.38	$45.40	$45.40
Purchase #7	$134.31	6.484%	$143.0187	$143.02	$143.00	$143.00
7 purchase totals =	$1,034.10		$1,123.0649	$1,123.07	$1,123.00	$1,123.20