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	$249.39	10.504%	$275.5859	$275.59	$275.60	$275.60
Purchase #2	$40.85	12.231%	$45.8464	$45.85	$45.85	$45.80
Purchase #3	$164.90	12.327%	$185.2272	$185.23	$185.25	$185.20
Purchase #4	$226.96	3.195%	$234.2114	$234.21	$234.20	$234.20
Purchase #5	$139.75	4.569%	$146.1352	$146.14	$146.15	$146.10
Purchase #6	$13.52	13.235%	$15.3094	$15.31	$15.30	$15.30
Purchase #7	$101.50	7.305%	$108.9146	$108.91	$108.90	$108.90
7 purchase totals =	$936.87		$1,011.2301	$1,011.24	$1,011.25	$1,011.10