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	$196.40	13.345%	$222.6096	$222.61	$222.60	$222.60
Purchase #2	$118.96	7.131%	$127.443	$127.44	$127.45	$127.40
Purchase #3	$143.52	12.511%	$161.4758	$161.48	$161.50	$161.50
Purchase #4	$18.83	4.241%	$19.6286	$19.63	$19.65	$19.60
Purchase #5	$148.69	8.106%	$160.7428	$160.74	$160.75	$160.70
Purchase #6	$224.28	7.350%	$240.7646	$240.76	$240.75	$240.80
Purchase #7	$45.50	13.246%	$51.5269	$51.53	$51.55	$51.50
7 purchase totals =	$896.18		$984.1913	$984.19	$984.25	$984.10