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	$106.38	6.385%	$113.1724	$113.17	$113.15	$113.20
Purchase #2	$69.75	3.786%	$72.3907	$72.39	$72.40	$72.40
Purchase #3	$72.83	10.681%	$80.609	$80.61	$80.60	$80.60
Purchase #4	$90.75	13.385%	$102.8969	$102.90	$102.90	$102.90
Purchase #5	$245.42	5.503%	$258.9255	$258.93	$258.95	$258.90
Purchase #6	$155.85	10.504%	$172.2205	$172.22	$172.20	$172.20
Purchase #7	$159.93	7.622%	$172.1199	$172.12	$172.10	$172.10
7 purchase totals =	$900.91		$972.3349	$972.34	$972.30	$972.30