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	$26.65	13.555%	$30.2624	$30.26	$30.25	$30.30
Purchase #2	$52.89	11.686%	$59.0707	$59.07	$59.05	$59.10
Purchase #3	$72.67	12.433%	$81.7051	$81.71	$81.70	$81.70
Purchase #4	$103.49	7.288%	$111.0324	$111.03	$111.05	$111.00
Purchase #5	$213.77	4.151%	$222.6436	$222.64	$222.65	$222.60
Purchase #6	$200.53	7.316%	$215.2008	$215.20	$215.20	$215.20
Purchase #7	$92.67	7.516%	$99.6351	$99.64	$99.65	$99.60
7 purchase totals =	$762.67		$819.5501	$819.55	$819.55	$819.50