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	$20.94	7.483%	$22.5069	$22.51	$22.50	$22.50
Purchase #2	$27.60	12.781%	$31.1276	$31.13	$31.15	$31.10
Purchase #3	$82.57	3.570%	$85.5177	$85.52	$85.50	$85.50
Purchase #4	$119.64	4.328%	$124.818	$124.82	$124.80	$124.80
Purchase #5	$184.34	10.401%	$203.5132	$203.51	$203.50	$203.50
Purchase #6	$87.91	10.362%	$97.0192	$97.02	$97.00	$97.00
Purchase #7	$149.42	10.592%	$165.2466	$165.25	$165.25	$165.20
7 purchase totals =	$672.42		$729.7492	$729.76	$729.70	$729.60