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	$221.43	3.823%	$229.8953	$229.90	$229.90	$229.90
Purchase #2	$190.65	10.398%	$210.4738	$210.47	$210.45	$210.50
Purchase #3	$56.43	7.382%	$60.5957	$60.60	$60.60	$60.60
Purchase #4	$78.81	5.860%	$83.4283	$83.43	$83.45	$83.40
Purchase #5	$205.96	9.630%	$225.7939	$225.79	$225.80	$225.80
Purchase #6	$180.55	13.632%	$205.1626	$205.16	$205.15	$205.20
Purchase #7	$31.44	9.679%	$34.4831	$34.48	$34.50	$34.50
7 purchase totals =	$965.27		$1,049.8327	$1,049.83	$1,049.85	$1,049.90