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	$187.82	3.750%	$194.8633	$194.86	$194.85	$194.90
Purchase #2	$194.65	9.351%	$212.8517	$212.85	$212.85	$212.90
Purchase #3	$203.74	8.233%	$220.5139	$220.51	$220.50	$220.50
Purchase #4	$58.98	4.159%	$61.433	$61.43	$61.45	$61.40
Purchase #5	$39.70	13.782%	$45.1715	$45.17	$45.15	$45.20
Purchase #6	$45.35	11.547%	$50.5866	$50.59	$50.60	$50.60
Purchase #7	$39.79	13.844%	$45.2985	$45.30	$45.30	$45.30
7 purchase totals =	$770.03		$830.7185	$830.71	$830.70	$830.80