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	$65.58	10.788%	$72.6548	$72.65	$72.65	$72.70
Purchase #2	$249.54	6.729%	$266.3315	$266.33	$266.35	$266.30
Purchase #3	$47.66	13.605%	$54.1441	$54.14	$54.15	$54.10
Purchase #4	$43.67	4.587%	$45.6731	$45.67	$45.65	$45.70
Purchase #5	$91.51	10.383%	$101.0115	$101.01	$101.00	$101.00
Purchase #6	$159.34	3.621%	$165.1097	$165.11	$165.10	$165.10
Purchase #7	$137.91	12.819%	$155.5887	$155.59	$155.60	$155.60
7 purchase totals =	$795.21		$860.5134	$860.50	$860.50	$860.50