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	$59.67	9.481%	$65.3273	$65.33	$65.35	$65.30
Purchase #2	$189.37	10.236%	$208.7539	$208.75	$208.75	$208.80
Purchase #3	$232.38	10.341%	$256.4104	$256.41	$256.40	$256.40
Purchase #4	$52.38	13.684%	$59.5477	$59.55	$59.55	$59.50
Purchase #5	$199.79	3.672%	$207.1263	$207.13	$207.15	$207.10
Purchase #6	$67.34	7.577%	$72.4424	$72.44	$72.45	$72.40
Purchase #7	$87.73	11.791%	$98.0742	$98.07	$98.05	$98.10
7 purchase totals =	$888.66		$967.6822	$967.68	$967.70	$967.60