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	$55.82	13.402%	$63.301	$63.30	$63.30	$63.30
Purchase #2	$202.35	13.475%	$229.6167	$229.62	$229.60	$229.60
Purchase #3	$116.89	13.680%	$132.8806	$132.88	$132.90	$132.90
Purchase #4	$77.65	7.578%	$83.5343	$83.53	$83.55	$83.50
Purchase #5	$150.77	13.312%	$170.8405	$170.84	$170.85	$170.80
Purchase #6	$160.31	5.282%	$168.7776	$168.78	$168.80	$168.80
Purchase #7	$88.30	13.500%	$100.2205	$100.22	$100.20	$100.20
7 purchase totals =	$852.09		$949.1712	$949.17	$949.20	$949.10