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	$110.54	5.322%	$116.4229	$116.42	$116.40	$116.40
Purchase #2	$64.28	13.477%	$72.943	$72.94	$72.95	$72.90
Purchase #3	$37.54	3.457%	$38.8378	$38.84	$38.85	$38.80
Purchase #4	$188.51	3.534%	$195.1719	$195.17	$195.15	$195.20
Purchase #5	$149.71	5.467%	$157.8946	$157.89	$157.90	$157.90
Purchase #6	$213.60	7.735%	$230.122	$230.12	$230.10	$230.10
Purchase #7	$177.67	8.352%	$192.509	$192.51	$192.50	$192.50
7 purchase totals =	$941.85		$1,003.9012	$1,003.89	$1,003.85	$1,003.80