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	$131.55	10.546%	$145.4233	$145.42	$145.40	$145.40
Purchase #2	$225.34	3.514%	$233.2584	$233.26	$233.25	$233.30
Purchase #3	$223.39	12.130%	$250.4872	$250.49	$250.50	$250.50
Purchase #4	$32.45	13.655%	$36.881	$36.88	$36.90	$36.90
Purchase #5	$91.42	6.564%	$97.4208	$97.42	$97.40	$97.40
Purchase #6	$17.92	3.268%	$18.5056	$18.51	$18.50	$18.50
Purchase #7	$78.47	6.541%	$83.6027	$83.60	$83.60	$83.60
7 purchase totals =	$800.54		$865.5790	$865.58	$865.55	$865.60