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	$34.66	7.530%	$37.2699	$37.27	$37.25	$37.30
Purchase #2	$56.46	3.806%	$58.6089	$58.61	$58.60	$58.60
Purchase #3	$24.79	3.788%	$25.729	$25.73	$25.75	$25.70
Purchase #4	$53.91	13.564%	$61.2224	$61.22	$61.20	$61.20
Purchase #5	$195.61	5.237%	$205.8541	$205.85	$205.85	$205.90
Purchase #6	$46.49	4.285%	$48.4821	$48.48	$48.50	$48.50
Purchase #7	$241.34	13.391%	$273.6578	$273.66	$273.65	$273.70
7 purchase totals =	$653.26		$710.8242	$710.82	$710.80	$710.90