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	$42.66	8.748%	$46.3919	$46.39	$46.40	$46.40
Purchase #2	$133.74	6.153%	$141.969	$141.97	$141.95	$142.00
Purchase #3	$217.39	6.280%	$231.0421	$231.04	$231.05	$231.00
Purchase #4	$69.48	13.110%	$78.5888	$78.59	$78.60	$78.60
Purchase #5	$48.29	11.218%	$53.7072	$53.71	$53.70	$53.70
Purchase #6	$36.92	6.150%	$39.1906	$39.19	$39.20	$39.20
Purchase #7	$76.45	5.804%	$80.8872	$80.89	$80.90	$80.90
7 purchase totals =	$624.93		$671.7768	$671.78	$671.80	$671.80