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	$84.29	8.729%	$91.6477	$91.65	$91.65	$91.60
Purchase #2	$161.54	6.633%	$172.2549	$172.25	$172.25	$172.30
Purchase #3	$221.85	10.248%	$244.5852	$244.59	$244.60	$244.60
Purchase #4	$230.69	4.857%	$241.8946	$241.89	$241.90	$241.90
Purchase #5	$71.67	13.273%	$81.1828	$81.18	$81.20	$81.20
Purchase #6	$39.61	12.285%	$44.4761	$44.48	$44.50	$44.50
Purchase #7	$53.46	10.525%	$59.0867	$59.09	$59.10	$59.10
7 purchase totals =	$863.11		$935.1280	$935.13	$935.20	$935.20