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	$245.67	7.672%	$264.5178	$264.52	$264.50	$264.50
Purchase #2	$43.52	3.197%	$44.9113	$44.91	$44.90	$44.90
Purchase #3	$137.92	10.865%	$152.905	$152.91	$152.90	$152.90
Purchase #4	$240.25	7.427%	$258.0934	$258.09	$258.10	$258.10
Purchase #5	$115.52	3.233%	$119.2548	$119.25	$119.25	$119.30
Purchase #6	$35.44	13.481%	$40.2177	$40.22	$40.20	$40.20
Purchase #7	$173.36	10.763%	$192.0187	$192.02	$192.00	$192.00
7 purchase totals =	$991.68		$1,071.9187	$1,071.92	$1,071.85	$1,071.90