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	$97.54	13.262%	$110.4758	$110.48	$110.50	$110.50
Purchase #2	$159.42	10.105%	$175.5294	$175.53	$175.55	$175.50
Purchase #3	$208.57	4.252%	$217.4384	$217.44	$217.45	$217.40
Purchase #4	$156.76	9.874%	$172.2385	$172.24	$172.25	$172.20
Purchase #5	$31.72	12.796%	$35.7789	$35.78	$35.80	$35.80
Purchase #6	$153.59	3.675%	$159.2344	$159.23	$159.25	$159.20
Purchase #7	$221.53	7.848%	$238.9157	$238.92	$238.90	$238.90
7 purchase totals =	$1,029.13		$1,109.6111	$1,109.62	$1,109.70	$1,109.50