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	$171.83	13.762%	$195.4772	$195.48	$195.50	$195.50
Purchase #2	$197.31	7.275%	$211.6643	$211.66	$211.65	$211.70
Purchase #3	$94.71	5.475%	$99.8954	$99.90	$99.90	$99.90
Purchase #4	$39.39	3.472%	$40.7576	$40.76	$40.75	$40.80
Purchase #5	$8.58	3.685%	$8.8962	$8.90	$8.90	$8.90
Purchase #6	$100.56	11.287%	$111.9102	$111.91	$111.90	$111.90
Purchase #7	$185.35	3.655%	$192.1245	$192.12	$192.10	$192.10
7 purchase totals =	$797.73		$860.7254	$860.73	$860.70	$860.80