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	$229.48	13.449%	$260.3428	$260.34	$260.35	$260.30
Purchase #2	$208.72	7.487%	$224.3469	$224.35	$224.35	$224.30
Purchase #3	$109.53	12.369%	$123.0778	$123.08	$123.10	$123.10
Purchase #4	$88.73	13.382%	$100.6038	$100.60	$100.60	$100.60
Purchase #5	$225.83	6.328%	$240.1205	$240.12	$240.10	$240.10
Purchase #6	$244.84	12.344%	$275.063	$275.06	$275.05	$275.10
Purchase #7	$244.44	3.510%	$253.0198	$253.02	$253.00	$253.00
7 purchase totals =	$1,351.57		$1,476.5746	$1,476.57	$1,476.55	$1,476.50