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	$206.70	7.505%	$222.2128	$222.21	$222.20	$222.20
Purchase #2	$149.94	11.240%	$166.7933	$166.79	$166.80	$166.80
Purchase #3	$13.41	3.379%	$13.8631	$13.86	$13.85	$13.90
Purchase #4	$236.26	4.415%	$246.6909	$246.69	$246.70	$246.70
Purchase #5	$71.27	10.168%	$78.5167	$78.52	$78.50	$78.50
Purchase #6	$142.72	6.184%	$151.5458	$151.55	$151.55	$151.50
Purchase #7	$28.70	12.329%	$32.2384	$32.24	$32.25	$32.20
7 purchase totals =	$849.00		$911.8610	$911.86	$911.85	$911.80