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	$212.35	6.325%	$225.7811	$225.78	$225.80	$225.80
Purchase #2	$64.47	13.822%	$73.381	$73.38	$73.40	$73.40
Purchase #3	$63.79	4.300%	$66.533	$66.53	$66.55	$66.50
Purchase #4	$6.69	10.459%	$7.3897	$7.39	$7.40	$7.40
Purchase #5	$233.79	13.408%	$265.1366	$265.14	$265.15	$265.10
Purchase #6	$129.65	6.426%	$137.9813	$137.98	$138.00	$138.00
Purchase #7	$82.38	9.159%	$89.9252	$89.93	$89.95	$89.90
7 purchase totals =	$793.12		$866.1279	$866.13	$866.25	$866.10