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	$192.29	13.622%	$218.4837	$218.48	$218.50	$218.50
Purchase #2	$158.30	8.477%	$171.7191	$171.72	$171.70	$171.70
Purchase #3	$92.45	8.355%	$100.1742	$100.17	$100.15	$100.20
Purchase #4	$12.90	8.568%	$14.0053	$14.01	$14.00	$14.00
Purchase #5	$56.59	11.821%	$63.2795	$63.28	$63.30	$63.30
Purchase #6	$88.34	12.671%	$99.5336	$99.53	$99.55	$99.50
Purchase #7	$58.75	9.569%	$64.3718	$64.37	$64.35	$64.40
7 purchase totals =	$659.62		$731.5672	$731.56	$731.55	$731.60