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	$232.43	6.574%	$247.7099	$247.71	$247.70	$247.70
Purchase #2	$145.59	3.295%	$150.3872	$150.39	$150.40	$150.40
Purchase #3	$58.37	13.473%	$66.2342	$66.23	$66.25	$66.20
Purchase #4	$158.60	8.712%	$172.4172	$172.42	$172.40	$172.40
Purchase #5	$68.91	3.246%	$71.1468	$71.15	$71.15	$71.10
Purchase #6	$192.48	5.108%	$202.3119	$202.31	$202.30	$202.30
Purchase #7	$66.39	9.806%	$72.9002	$72.90	$72.90	$72.90
7 purchase totals =	$922.77		$983.1074	$983.11	$983.10	$983.00