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	$95.89	8.315%	$103.8633	$103.86	$103.85	$103.90
Purchase #2	$175.40	9.378%	$191.849	$191.85	$191.85	$191.80
Purchase #3	$247.59	3.421%	$256.0601	$256.06	$256.05	$256.10
Purchase #4	$91.99	8.378%	$99.6969	$99.70	$99.70	$99.70
Purchase #5	$234.76	5.821%	$248.4254	$248.43	$248.45	$248.40
Purchase #6	$214.73	5.136%	$225.7585	$225.76	$225.75	$225.80
Purchase #7	$203.46	5.472%	$214.5933	$214.59	$214.60	$214.60
7 purchase totals =	$1,263.82		$1,340.2465	$1,340.25	$1,340.25	$1,340.30