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	$202.56	3.166%	$208.973	$208.97	$208.95	$209.00
Purchase #2	$55.55	6.344%	$59.0741	$59.07	$59.05	$59.10
Purchase #3	$150.59	4.628%	$157.5593	$157.56	$157.55	$157.60
Purchase #4	$128.61	8.431%	$139.4531	$139.45	$139.45	$139.50
Purchase #5	$59.39	6.359%	$63.1666	$63.17	$63.15	$63.20
Purchase #6	$141.96	11.763%	$158.6588	$158.66	$158.65	$158.70
Purchase #7	$82.35	10.399%	$90.9136	$90.91	$90.90	$90.90
7 purchase totals =	$821.01		$877.7985	$877.79	$877.70	$878.00