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	$50.44	5.873%	$53.4023	$53.40	$53.40	$53.40
Purchase #2	$132.90	10.178%	$146.4266	$146.43	$146.45	$146.40
Purchase #3	$27.69	13.795%	$31.5098	$31.51	$31.50	$31.50
Purchase #4	$155.31	4.831%	$162.813	$162.81	$162.80	$162.80
Purchase #5	$200.32	3.143%	$206.6161	$206.62	$206.60	$206.60
Purchase #6	$21.38	3.570%	$22.1433	$22.14	$22.15	$22.10
Purchase #7	$9.96	3.847%	$10.3432	$10.34	$10.35	$10.30
7 purchase totals =	$598.00		$633.2543	$633.25	$633.25	$633.10