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	$213.41	11.782%	$238.554	$238.55	$238.55	$238.60
Purchase #2	$249.46	8.674%	$271.0982	$271.10	$271.10	$271.10
Purchase #3	$246.65	4.255%	$257.145	$257.15	$257.15	$257.10
Purchase #4	$64.68	10.503%	$71.4733	$71.47	$71.45	$71.50
Purchase #5	$69.43	5.835%	$73.4812	$73.48	$73.50	$73.50
Purchase #6	$29.84	13.654%	$33.9144	$33.91	$33.90	$33.90
Purchase #7	$200.38	13.391%	$227.2129	$227.21	$227.20	$227.20
7 purchase totals =	$1,073.85		$1,172.8790	$1,172.87	$1,172.85	$1,172.90