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	$130.46	3.308%	$134.7756	$134.78	$134.80	$134.80
Purchase #2	$155.61	8.282%	$168.4976	$168.50	$168.50	$168.50
Purchase #3	$132.94	5.378%	$140.0895	$140.09	$140.10	$140.10
Purchase #4	$34.40	13.799%	$39.1469	$39.15	$39.15	$39.10
Purchase #5	$231.29	8.139%	$250.1147	$250.11	$250.10	$250.10
Purchase #6	$19.30	5.229%	$20.3092	$20.31	$20.30	$20.30
Purchase #7	$188.45	12.748%	$212.4736	$212.47	$212.45	$212.50
7 purchase totals =	$892.45		$965.4071	$965.41	$965.40	$965.40