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	$199.30	7.146%	$213.542	$213.54	$213.55	$213.50
Purchase #2	$70.89	9.366%	$77.5296	$77.53	$77.55	$77.50
Purchase #3	$87.67	7.815%	$94.5214	$94.52	$94.50	$94.50
Purchase #4	$134.54	3.506%	$139.257	$139.26	$139.25	$139.30
Purchase #5	$247.93	3.292%	$256.0919	$256.09	$256.10	$256.10
Purchase #6	$75.98	10.259%	$83.7748	$83.77	$83.75	$83.80
Purchase #7	$38.72	10.612%	$42.829	$42.83	$42.85	$42.80
7 purchase totals =	$855.03		$907.5457	$907.54	$907.55	$907.50