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	9.520%	$143.9969	$144.00	$144.00	$144.00
Purchase #2	$11.51	13.865%	$13.1059	$13.11	$13.10	$13.10
Purchase #3	$170.76	13.104%	$193.1364	$193.14	$193.15	$193.10
Purchase #4	$217.85	3.110%	$224.6251	$224.63	$224.65	$224.60
Purchase #5	$85.88	5.313%	$90.4428	$90.44	$90.45	$90.40
Purchase #6	$97.63	11.722%	$109.0742	$109.07	$109.05	$109.10
Purchase #7	$116.36	12.697%	$131.1342	$131.13	$131.15	$131.10
7 purchase totals =	$831.47		$905.5155	$905.52	$905.55	$905.40