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	$57.38	3.576%	$59.4319	$59.43	$59.45	$59.40
Purchase #2	$126.74	13.734%	$144.1465	$144.15	$144.15	$144.10
Purchase #3	$32.39	12.170%	$36.3319	$36.33	$36.35	$36.30
Purchase #4	$6.50	6.249%	$6.9062	$6.91	$6.90	$6.90
Purchase #5	$5.83	12.512%	$6.5594	$6.56	$6.55	$6.60
Purchase #6	$159.64	8.521%	$173.2429	$173.24	$173.25	$173.20
Purchase #7	$29.37	5.683%	$31.0391	$31.04	$31.05	$31.00
7 purchase totals =	$417.85		$457.6579	$457.66	$457.70	$457.50