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	$190.48	9.415%	$208.4137	$208.41	$208.40	$208.40
Purchase #2	$197.33	13.750%	$224.4629	$224.46	$224.45	$224.50
Purchase #3	$84.72	6.707%	$90.4022	$90.40	$90.40	$90.40
Purchase #4	$77.34	4.714%	$80.9858	$80.99	$81.00	$81.00
Purchase #5	$54.85	8.103%	$59.2945	$59.29	$59.30	$59.30
Purchase #6	$78.44	6.378%	$83.4429	$83.44	$83.45	$83.40
Purchase #7	$150.89	5.199%	$158.7348	$158.73	$158.75	$158.70
7 purchase totals =	$834.05		$905.7368	$905.72	$905.75	$905.70