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	$141.25	13.721%	$160.6309	$160.63	$160.65	$160.60
Purchase #2	$24.42	5.329%	$25.7213	$25.72	$25.70	$25.70
Purchase #3	$141.69	6.809%	$151.3377	$151.34	$151.35	$151.30
Purchase #4	$146.42	8.508%	$158.8774	$158.88	$158.90	$158.90
Purchase #5	$137.71	5.215%	$144.8916	$144.89	$144.90	$144.90
Purchase #6	$100.96	9.380%	$110.43	$110.43	$110.45	$110.40
Purchase #7	$142.89	3.165%	$147.4125	$147.41	$147.40	$147.40
7 purchase totals =	$835.34		$899.3014	$899.30	$899.35	$899.20