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	$107.63	4.208%	$112.1591	$112.16	$112.15	$112.20
Purchase #2	$166.78	3.316%	$172.3104	$172.31	$172.30	$172.30
Purchase #3	$130.85	8.430%	$141.8807	$141.88	$141.90	$141.90
Purchase #4	$86.45	9.672%	$94.8114	$94.81	$94.80	$94.80
Purchase #5	$107.46	4.754%	$112.5686	$112.57	$112.55	$112.60
Purchase #6	$163.47	3.708%	$169.5315	$169.53	$169.55	$169.50
Purchase #7	$235.51	9.668%	$258.2791	$258.28	$258.30	$258.30
7 purchase totals =	$998.15		$1,061.5408	$1,061.54	$1,061.55	$1,061.60