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	$44.70	4.502%	$46.7124	$46.71	$46.70	$46.70
Purchase #2	$117.71	4.568%	$123.087	$123.09	$123.10	$123.10
Purchase #3	$148.63	6.227%	$157.8852	$157.89	$157.90	$157.90
Purchase #4	$74.95	4.215%	$78.1091	$78.11	$78.10	$78.10
Purchase #5	$32.82	10.537%	$36.2782	$36.28	$36.30	$36.30
Purchase #6	$76.51	13.191%	$86.6024	$86.60	$86.60	$86.60
Purchase #7	$82.58	9.300%	$90.2599	$90.26	$90.25	$90.30
7 purchase totals =	$577.90		$618.9342	$618.94	$618.95	$619.00