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	$210.71	5.574%	$222.455	$222.46	$222.45	$222.50
Purchase #2	$45.64	11.309%	$50.8014	$50.80	$50.80	$50.80
Purchase #3	$21.98	7.194%	$23.5612	$23.56	$23.55	$23.60
Purchase #4	$87.68	11.595%	$97.8465	$97.85	$97.85	$97.80
Purchase #5	$152.98	7.250%	$164.0711	$164.07	$164.05	$164.10
Purchase #6	$20.89	4.310%	$21.7904	$21.79	$21.80	$21.80
Purchase #7	$227.77	12.235%	$255.6377	$255.64	$255.65	$255.60
7 purchase totals =	$767.65		$836.1633	$836.17	$836.15	$836.20