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	$166.59	8.186%	$180.2271	$180.23	$180.25	$180.20
Purchase #2	$67.89	6.578%	$72.3558	$72.36	$72.35	$72.40
Purchase #3	$238.91	13.678%	$271.5881	$271.59	$271.60	$271.60
Purchase #4	$35.82	4.496%	$37.4305	$37.43	$37.45	$37.40
Purchase #5	$125.42	4.591%	$131.178	$131.18	$131.20	$131.20
Purchase #6	$152.25	6.867%	$162.705	$162.71	$162.70	$162.70
Purchase #7	$36.30	10.594%	$40.1456	$40.15	$40.15	$40.10
7 purchase totals =	$823.18		$895.6301	$895.65	$895.70	$895.60