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	$90.35	8.738%	$98.2448	$98.24	$98.25	$98.20
Purchase #2	$84.28	7.108%	$90.2706	$90.27	$90.25	$90.30
Purchase #3	$170.84	8.817%	$185.903	$185.90	$185.90	$185.90
Purchase #4	$62.47	12.385%	$70.2069	$70.21	$70.20	$70.20
Purchase #5	$39.81	6.102%	$42.2392	$42.24	$42.25	$42.20
Purchase #6	$236.62	8.130%	$255.8572	$255.86	$255.85	$255.90
Purchase #7	$193.94	3.468%	$200.6658	$200.67	$200.65	$200.70
7 purchase totals =	$878.31		$943.3875	$943.39	$943.35	$943.40