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	$225.31	11.348%	$250.8782	$250.88	$250.90	$250.90
Purchase #2	$216.39	13.153%	$244.8518	$244.85	$244.85	$244.90
Purchase #3	$199.52	3.700%	$206.9022	$206.90	$206.90	$206.90
Purchase #4	$140.92	7.874%	$152.016	$152.02	$152.00	$152.00
Purchase #5	$127.51	10.577%	$140.9967	$141.00	$141.00	$141.00
Purchase #6	$45.46	10.340%	$50.1606	$50.16	$50.15	$50.20
Purchase #7	$145.49	5.800%	$153.9284	$153.93	$153.95	$153.90
7 purchase totals =	$1,100.60		$1,199.7339	$1,199.74	$1,199.75	$1,199.80