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	$171.35	8.249%	$185.4847	$185.48	$185.50	$185.50
Purchase #2	$72.54	12.356%	$81.503	$81.50	$81.50	$81.50
Purchase #3	$23.27	4.580%	$24.3358	$24.34	$24.35	$24.30
Purchase #4	$10.43	12.174%	$11.6997	$11.70	$11.70	$11.70
Purchase #5	$64.45	12.483%	$72.4953	$72.50	$72.50	$72.50
Purchase #6	$193.47	10.328%	$213.4516	$213.45	$213.45	$213.50
Purchase #7	$157.25	4.461%	$164.2649	$164.26	$164.25	$164.30
7 purchase totals =	$692.76		$753.2350	$753.23	$753.25	$753.30