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	$189.80	5.663%	$200.5484	$200.55	$200.55	$200.50
Purchase #2	$65.85	10.179%	$72.5529	$72.55	$72.55	$72.60
Purchase #3	$160.76	11.788%	$179.7104	$179.71	$179.70	$179.70
Purchase #4	$95.89	13.496%	$108.8313	$108.83	$108.85	$108.80
Purchase #5	$86.26	4.576%	$90.2073	$90.21	$90.20	$90.20
Purchase #6	$77.79	3.654%	$80.6324	$80.63	$80.65	$80.60
Purchase #7	$208.58	3.339%	$215.5445	$215.54	$215.55	$215.50
7 purchase totals =	$884.93		$948.0272	$948.02	$948.05	$947.90