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	$66.74	6.596%	$71.1422	$71.14	$71.15	$71.10
Purchase #2	$11.44	7.355%	$12.2814	$12.28	$12.30	$12.30
Purchase #3	$68.66	5.554%	$72.4734	$72.47	$72.45	$72.50
Purchase #4	$64.62	12.185%	$72.4939	$72.49	$72.50	$72.50
Purchase #5	$8.79	4.252%	$9.1638	$9.16	$9.15	$9.20
Purchase #6	$141.61	3.428%	$146.4644	$146.46	$146.45	$146.50
Purchase #7	$140.77	6.149%	$149.4259	$149.43	$149.45	$149.40
7 purchase totals =	$502.63		$533.4450	$533.43	$533.45	$533.50