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	$235.35	7.665%	$253.3896	$253.39	$253.40	$253.40
Purchase #2	$210.47	3.242%	$217.2934	$217.29	$217.30	$217.30
Purchase #3	$176.67	4.408%	$184.4576	$184.46	$184.45	$184.50
Purchase #4	$125.78	8.484%	$136.4512	$136.45	$136.45	$136.50
Purchase #5	$200.59	12.519%	$225.7019	$225.70	$225.70	$225.70
Purchase #6	$109.42	7.142%	$117.2348	$117.23	$117.25	$117.20
Purchase #7	$123.26	3.244%	$127.2586	$127.26	$127.25	$127.30
7 purchase totals =	$1,181.54		$1,261.7871	$1,261.78	$1,261.80	$1,261.90