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	$77.44	10.702%	$85.7276	$85.73	$85.75	$85.70
Purchase #2	$155.89	9.302%	$170.3909	$170.39	$170.40	$170.40
Purchase #3	$83.26	13.874%	$94.8115	$94.81	$94.80	$94.80
Purchase #4	$83.95	7.577%	$90.3109	$90.31	$90.30	$90.30
Purchase #5	$250.49	6.591%	$266.9998	$267.00	$267.00	$267.00
Purchase #6	$81.56	4.782%	$85.4602	$85.46	$85.45	$85.50
Purchase #7	$37.80	4.244%	$39.4042	$39.40	$39.40	$39.40
7 purchase totals =	$770.39		$833.1051	$833.10	$833.10	$833.10