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	$164.81	9.183%	$179.9445	$179.94	$179.95	$179.90
Purchase #2	$81.25	3.180%	$83.8338	$83.83	$83.85	$83.80
Purchase #3	$67.29	7.848%	$72.5709	$72.57	$72.55	$72.60
Purchase #4	$67.31	5.309%	$70.8835	$70.88	$70.90	$70.90
Purchase #5	$126.51	13.366%	$143.4193	$143.42	$143.40	$143.40
Purchase #6	$81.50	5.707%	$86.1512	$86.15	$86.15	$86.20
Purchase #7	$38.88	4.483%	$40.623	$40.62	$40.60	$40.60
7 purchase totals =	$627.55		$677.4262	$677.41	$677.40	$677.40