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	$213.51	6.590%	$227.5803	$227.58	$227.60	$227.60
Purchase #2	$235.67	11.106%	$261.8435	$261.84	$261.85	$261.80
Purchase #3	$77.56	4.618%	$81.1417	$81.14	$81.15	$81.10
Purchase #4	$40.70	6.839%	$43.4835	$43.48	$43.50	$43.50
Purchase #5	$144.41	11.411%	$160.8886	$160.89	$160.90	$160.90
Purchase #6	$140.35	9.762%	$154.051	$154.05	$154.05	$154.10
Purchase #7	$166.38	4.605%	$174.0418	$174.04	$174.05	$174.00
7 purchase totals =	$1,018.58		$1,103.0304	$1,103.02	$1,103.10	$1,103.00