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	$65.47	8.604%	$71.103	$71.10	$71.10	$71.10
Purchase #2	$246.33	7.421%	$264.6101	$264.61	$264.60	$264.60
Purchase #3	$34.64	9.522%	$37.9384	$37.94	$37.95	$37.90
Purchase #4	$78.25	9.303%	$85.5296	$85.53	$85.55	$85.50
Purchase #5	$107.85	8.241%	$116.7379	$116.74	$116.75	$116.70
Purchase #6	$155.46	9.735%	$170.594	$170.59	$170.60	$170.60
Purchase #7	$199.83	4.697%	$209.216	$209.22	$209.20	$209.20
7 purchase totals =	$887.83		$955.7290	$955.73	$955.75	$955.60