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	$132.31	9.462%	$144.8292	$144.83	$144.85	$144.80
Purchase #2	$165.46	10.291%	$182.4875	$182.49	$182.50	$182.50
Purchase #3	$134.70	5.266%	$141.7933	$141.79	$141.80	$141.80
Purchase #4	$40.89	10.592%	$45.2211	$45.22	$45.20	$45.20
Purchase #5	$189.75	9.675%	$208.1083	$208.11	$208.10	$208.10
Purchase #6	$135.44	10.357%	$149.4675	$149.47	$149.45	$149.50
Purchase #7	$57.85	3.511%	$59.8811	$59.88	$59.90	$59.90
7 purchase totals =	$856.40		$931.7880	$931.79	$931.80	$931.80