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	$131.48	5.439%	$138.6312	$138.63	$138.65	$138.60
Purchase #2	$18.96	13.692%	$21.556	$21.56	$21.55	$21.60
Purchase #3	$76.85	13.318%	$87.0849	$87.08	$87.10	$87.10
Purchase #4	$139.82	4.613%	$146.2699	$146.27	$146.25	$146.30
Purchase #5	$185.93	3.572%	$192.5714	$192.57	$192.55	$192.60
Purchase #6	$228.77	4.241%	$238.4721	$238.47	$238.45	$238.50
Purchase #7	$164.70	4.499%	$172.1099	$172.11	$172.10	$172.10
7 purchase totals =	$946.51		$996.6954	$996.69	$996.65	$996.80