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	$66.37	9.582%	$72.7296	$72.73	$72.75	$72.70
Purchase #2	$221.77	5.128%	$233.1424	$233.14	$233.15	$233.10
Purchase #3	$120.32	10.632%	$133.1124	$133.11	$133.10	$133.10
Purchase #4	$138.71	5.106%	$145.7925	$145.79	$145.80	$145.80
Purchase #5	$200.27	13.420%	$227.1462	$227.15	$227.15	$227.10
Purchase #6	$234.85	12.520%	$264.2532	$264.25	$264.25	$264.30
Purchase #7	$213.25	5.736%	$225.482	$225.48	$225.50	$225.50
7 purchase totals =	$1,195.54		$1,301.6583	$1,301.65	$1,301.70	$1,301.60