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	$40.59	4.450%	$42.3963	$42.40	$42.40	$42.40
Purchase #2	$158.96	4.550%	$166.1927	$166.19	$166.20	$166.20
Purchase #3	$27.38	11.315%	$30.478	$30.48	$30.50	$30.50
Purchase #4	$35.90	12.644%	$40.4392	$40.44	$40.45	$40.40
Purchase #5	$48.72	6.842%	$52.0534	$52.05	$52.05	$52.10
Purchase #6	$66.34	9.774%	$72.8241	$72.82	$72.80	$72.80
Purchase #7	$235.60	5.827%	$249.3284	$249.33	$249.35	$249.30
7 purchase totals =	$613.49		$653.7121	$653.71	$653.75	$653.70