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	$207.58	7.693%	$223.5491	$223.55	$223.55	$223.50
Purchase #2	$62.56	3.707%	$64.8791	$64.88	$64.90	$64.90
Purchase #3	$151.29	11.483%	$168.6626	$168.66	$168.65	$168.70
Purchase #4	$12.81	10.233%	$14.1208	$14.12	$14.10	$14.10
Purchase #5	$135.58	3.858%	$140.8107	$140.81	$140.80	$140.80
Purchase #6	$67.61	4.622%	$70.7349	$70.73	$70.75	$70.70
Purchase #7	$100.37	13.427%	$113.8467	$113.85	$113.85	$113.80
7 purchase totals =	$737.80		$796.6039	$796.60	$796.60	$796.50