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	$223.40	3.560%	$231.353	$231.35	$231.35	$231.40
Purchase #2	$114.57	7.546%	$123.2155	$123.22	$123.20	$123.20
Purchase #3	$217.31	11.866%	$243.096	$243.10	$243.10	$243.10
Purchase #4	$172.43	4.248%	$179.7548	$179.75	$179.75	$179.80
Purchase #5	$153.32	10.735%	$169.7789	$169.78	$169.80	$169.80
Purchase #6	$94.49	11.234%	$105.105	$105.11	$105.10	$105.10
Purchase #7	$248.46	11.296%	$276.526	$276.53	$276.55	$276.50
7 purchase totals =	$1,223.98		$1,328.8292	$1,328.84	$1,328.85	$1,328.90