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	$160.60	12.462%	$180.614	$180.61	$180.60	$180.60
Purchase #2	$41.74	4.447%	$43.5962	$43.60	$43.60	$43.60
Purchase #3	$128.36	8.820%	$139.6814	$139.68	$139.70	$139.70
Purchase #4	$86.51	10.188%	$95.3236	$95.32	$95.30	$95.30
Purchase #5	$115.31	8.113%	$124.6651	$124.67	$124.65	$124.70
Purchase #6	$99.35	12.301%	$111.571	$111.57	$111.55	$111.60
Purchase #7	$188.29	8.325%	$203.9651	$203.97	$203.95	$204.00
7 purchase totals =	$820.16		$899.4164	$899.42	$899.35	$899.50