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	$81.78	7.635%	$88.0239	$88.02	$88.00	$88.00
Purchase #2	$139.99	11.309%	$155.8215	$155.82	$155.80	$155.80
Purchase #3	$150.94	13.218%	$170.8912	$170.89	$170.90	$170.90
Purchase #4	$17.40	11.613%	$19.4207	$19.42	$19.40	$19.40
Purchase #5	$140.28	4.447%	$146.5183	$146.52	$146.50	$146.50
Purchase #6	$233.26	10.125%	$256.8776	$256.88	$256.90	$256.90
Purchase #7	$210.43	5.612%	$222.2393	$222.24	$222.25	$222.20
7 purchase totals =	$974.08		$1,059.7925	$1,059.79	$1,059.75	$1,059.70