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	$44.71	4.111%	$46.548	$46.55	$46.55	$46.50
Purchase #2	$105.80	13.345%	$119.919	$119.92	$119.90	$119.90
Purchase #3	$42.80	6.443%	$45.5576	$45.56	$45.55	$45.60
Purchase #4	$48.77	7.750%	$52.5497	$52.55	$52.55	$52.50
Purchase #5	$63.94	3.608%	$66.247	$66.25	$66.25	$66.20
Purchase #6	$132.53	3.505%	$137.1752	$137.18	$137.20	$137.20
Purchase #7	$168.69	3.765%	$175.0412	$175.04	$175.05	$175.00
7 purchase totals =	$607.24		$643.0377	$643.05	$643.05	$642.90