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	$145.37	13.472%	$164.9542	$164.95	$164.95	$165.00
Purchase #2	$102.53	8.487%	$111.2317	$111.23	$111.25	$111.20
Purchase #3	$58.25	11.638%	$65.0291	$65.03	$65.05	$65.00
Purchase #4	$18.47	11.174%	$20.5338	$20.53	$20.55	$20.50
Purchase #5	$193.60	12.703%	$218.193	$218.19	$218.20	$218.20
Purchase #6	$28.56	9.636%	$31.312	$31.31	$31.30	$31.30
Purchase #7	$76.58	13.457%	$86.8854	$86.89	$86.90	$86.90
7 purchase totals =	$623.36		$698.1392	$698.13	$698.20	$698.10