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	$160.38	4.872%	$168.1937	$168.19	$168.20	$168.20
Purchase #2	$139.38	5.810%	$147.478	$147.48	$147.50	$147.50
Purchase #3	$160.61	8.152%	$173.7029	$173.70	$173.70	$173.70
Purchase #4	$109.47	13.217%	$123.9386	$123.94	$123.95	$123.90
Purchase #5	$52.59	3.683%	$54.5269	$54.53	$54.55	$54.50
Purchase #6	$109.53	7.749%	$118.0175	$118.02	$118.00	$118.00
Purchase #7	$147.42	10.662%	$163.1379	$163.14	$163.15	$163.10
7 purchase totals =	$879.38		$948.9955	$949.00	$949.05	$948.90