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	$86.33	9.356%	$94.407	$94.41	$94.40	$94.40
Purchase #2	$6.48	13.755%	$7.3713	$7.37	$7.35	$7.40
Purchase #3	$150.46	7.342%	$161.5068	$161.51	$161.50	$161.50
Purchase #4	$54.97	11.749%	$61.4284	$61.43	$61.45	$61.40
Purchase #5	$107.28	7.635%	$115.4708	$115.47	$115.45	$115.50
Purchase #6	$61.73	3.790%	$64.0696	$64.07	$64.05	$64.10
Purchase #7	$78.78	13.472%	$89.3932	$89.39	$89.40	$89.40
7 purchase totals =	$546.03		$593.6471	$593.65	$593.60	$593.70