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	$118.93	12.556%	$133.8629	$133.86	$133.85	$133.90
Purchase #2	$65.29	8.471%	$70.8207	$70.82	$70.80	$70.80
Purchase #3	$37.45	11.313%	$41.6867	$41.69	$41.70	$41.70
Purchase #4	$104.88	11.693%	$117.1436	$117.14	$117.15	$117.10
Purchase #5	$208.34	8.234%	$225.4947	$225.49	$225.50	$225.50
Purchase #6	$214.60	12.449%	$241.3156	$241.32	$241.30	$241.30
Purchase #7	$228.92	7.282%	$245.59	$245.59	$245.60	$245.60
7 purchase totals =	$978.41		$1,075.9142	$1,075.91	$1,075.90	$1,075.90