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	$248.29	6.429%	$264.2526	$264.25	$264.25	$264.30
Purchase #2	$214.73	4.801%	$225.0392	$225.04	$225.05	$225.00
Purchase #3	$41.38	8.316%	$44.8212	$44.82	$44.80	$44.80
Purchase #4	$177.69	5.738%	$187.8859	$187.89	$187.90	$187.90
Purchase #5	$98.55	5.669%	$104.1368	$104.14	$104.15	$104.10
Purchase #6	$74.46	11.575%	$83.0787	$83.08	$83.10	$83.10
Purchase #7	$138.79	10.325%	$153.1201	$153.12	$153.10	$153.10
7 purchase totals =	$993.89		$1,062.3345	$1,062.34	$1,062.35	$1,062.30