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	$63.35	3.413%	$65.5121	$65.51	$65.50	$65.50
Purchase #2	$203.66	13.591%	$231.3394	$231.34	$231.35	$231.30
Purchase #3	$8.70	7.243%	$9.3301	$9.33	$9.35	$9.30
Purchase #4	$168.62	6.383%	$179.383	$179.38	$179.40	$179.40
Purchase #5	$67.94	8.224%	$73.5274	$73.53	$73.55	$73.50
Purchase #6	$56.64	4.586%	$59.2375	$59.24	$59.25	$59.20
Purchase #7	$64.60	3.791%	$67.049	$67.05	$67.05	$67.00
7 purchase totals =	$633.51		$685.3785	$685.38	$685.45	$685.20