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	$14.53	3.736%	$15.0728	$15.07	$15.05	$15.10
Purchase #2	$53.63	11.151%	$59.6103	$59.61	$59.60	$59.60
Purchase #3	$7.79	10.593%	$8.6152	$8.62	$8.60	$8.60
Purchase #4	$176.37	13.687%	$200.5098	$200.51	$200.50	$200.50
Purchase #5	$26.53	11.359%	$29.5435	$29.54	$29.55	$29.50
Purchase #6	$80.78	10.636%	$89.3718	$89.37	$89.35	$89.40
Purchase #7	$45.78	3.680%	$47.4647	$47.46	$47.45	$47.50
7 purchase totals =	$405.41		$450.1881	$450.18	$450.10	$450.20