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	$20.37	10.493%	$22.5074	$22.51	$22.50	$22.50
Purchase #2	$200.43	4.528%	$209.5055	$209.51	$209.50	$209.50
Purchase #3	$139.79	8.460%	$151.6162	$151.62	$151.60	$151.60
Purchase #4	$230.48	5.468%	$243.0826	$243.08	$243.10	$243.10
Purchase #5	$210.51	5.497%	$222.0817	$222.08	$222.10	$222.10
Purchase #6	$38.98	11.736%	$43.5547	$43.55	$43.55	$43.60
Purchase #7	$191.55	13.464%	$217.3403	$217.34	$217.35	$217.30
7 purchase totals =	$1,032.11		$1,109.6884	$1,109.69	$1,109.70	$1,109.70