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	$247.30	3.330%	$255.5351	$255.54	$255.55	$255.50
Purchase #2	$225.32	13.217%	$255.1005	$255.10	$255.10	$255.10
Purchase #3	$135.92	11.796%	$151.9531	$151.95	$151.95	$152.00
Purchase #4	$189.77	11.489%	$211.5727	$211.57	$211.55	$211.60
Purchase #5	$61.69	7.129%	$66.0879	$66.09	$66.10	$66.10
Purchase #6	$100.78	5.280%	$106.1012	$106.10	$106.10	$106.10
Purchase #7	$86.45	10.297%	$95.3518	$95.35	$95.35	$95.40
7 purchase totals =	$1,047.23		$1,141.7023	$1,141.70	$1,141.70	$1,141.80