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	$61.71	7.236%	$66.1753	$66.18	$66.20	$66.20
Purchase #2	$22.36	9.514%	$24.4873	$24.49	$24.50	$24.50
Purchase #3	$27.82	13.573%	$31.596	$31.60	$31.60	$31.60
Purchase #4	$197.29	13.293%	$223.5158	$223.52	$223.50	$223.50
Purchase #5	$80.51	3.250%	$83.1266	$83.13	$83.15	$83.10
Purchase #6	$54.63	8.328%	$59.1796	$59.18	$59.20	$59.20
Purchase #7	$192.63	11.302%	$214.401	$214.40	$214.40	$214.40
7 purchase totals =	$636.95		$702.4816	$702.50	$702.55	$702.50