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	$120.44	9.328%	$131.6746	$131.67	$131.65	$131.70
Purchase #2	$65.56	10.292%	$72.3074	$72.31	$72.30	$72.30
Purchase #3	$90.54	12.264%	$101.6438	$101.64	$101.65	$101.60
Purchase #4	$158.91	9.176%	$173.4916	$173.49	$173.50	$173.50
Purchase #5	$250.57	8.674%	$272.3044	$272.30	$272.30	$272.30
Purchase #6	$172.82	11.580%	$192.8326	$192.83	$192.85	$192.80
Purchase #7	$81.39	5.827%	$86.1326	$86.13	$86.15	$86.10
7 purchase totals =	$940.23		$1,030.3870	$1,030.37	$1,030.40	$1,030.30