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	$105.37	5.678%	$111.3529	$111.35	$111.35	$111.40
Purchase #2	$137.42	11.631%	$153.4033	$153.40	$153.40	$153.40
Purchase #3	$203.91	10.359%	$225.033	$225.03	$225.05	$225.00
Purchase #4	$37.88	6.487%	$40.3373	$40.34	$40.35	$40.30
Purchase #5	$66.94	8.686%	$72.7544	$72.75	$72.75	$72.80
Purchase #6	$163.37	10.252%	$180.1187	$180.12	$180.10	$180.10
Purchase #7	$62.85	11.245%	$69.9175	$69.92	$69.90	$69.90
7 purchase totals =	$777.74		$852.9171	$852.91	$852.90	$852.90