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	$171.87	10.814%	$190.456	$190.46	$190.45	$190.50
Purchase #2	$80.59	6.704%	$85.9928	$85.99	$86.00	$86.00
Purchase #3	$165.88	4.172%	$172.8005	$172.80	$172.80	$172.80
Purchase #4	$61.49	7.696%	$66.2223	$66.22	$66.20	$66.20
Purchase #5	$61.84	9.672%	$67.8212	$67.82	$67.80	$67.80
Purchase #6	$149.59	4.837%	$156.8257	$156.83	$156.85	$156.80
Purchase #7	$150.57	5.342%	$158.6134	$158.61	$158.60	$158.60
7 purchase totals =	$841.83		$898.7319	$898.73	$898.70	$898.70