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	$45.37	3.164%	$46.8055	$46.81	$46.80	$46.80
Purchase #2	$141.45	5.105%	$148.671	$148.67	$148.65	$148.70
Purchase #3	$181.65	5.448%	$191.5463	$191.55	$191.55	$191.50
Purchase #4	$171.39	13.387%	$194.334	$194.33	$194.35	$194.30
Purchase #5	$223.89	8.555%	$243.0438	$243.04	$243.05	$243.00
Purchase #6	$234.91	13.458%	$266.5242	$266.52	$266.50	$266.50
Purchase #7	$114.66	7.854%	$123.6654	$123.67	$123.65	$123.70
7 purchase totals =	$1,113.32		$1,214.5902	$1,214.59	$1,214.55	$1,214.50