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	$219.56	6.453%	$233.7282	$233.73	$233.75	$233.70
Purchase #2	$248.51	4.687%	$260.1577	$260.16	$260.15	$260.20
Purchase #3	$75.77	6.179%	$80.4518	$80.45	$80.45	$80.50
Purchase #4	$138.53	10.253%	$152.7335	$152.73	$152.75	$152.70
Purchase #5	$109.30	13.389%	$123.9342	$123.93	$123.95	$123.90
Purchase #6	$13.26	8.822%	$14.4298	$14.43	$14.45	$14.40
Purchase #7	$227.27	10.232%	$250.5243	$250.52	$250.50	$250.50
7 purchase totals =	$1,032.20		$1,115.9595	$1,115.95	$1,116.00	$1,115.90