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	$86.56	12.231%	$97.1472	$97.15	$97.15	$97.10
Purchase #2	$219.48	6.239%	$233.1734	$233.17	$233.15	$233.20
Purchase #3	$217.35	3.227%	$224.3639	$224.36	$224.35	$224.40
Purchase #4	$124.77	4.600%	$130.5094	$130.51	$130.50	$130.50
Purchase #5	$228.37	11.837%	$255.4022	$255.40	$255.40	$255.40
Purchase #6	$242.52	3.284%	$250.4844	$250.48	$250.50	$250.50
Purchase #7	$59.95	7.665%	$64.5452	$64.55	$64.55	$64.50
7 purchase totals =	$1,179.00		$1,255.6257	$1,255.62	$1,255.60	$1,255.60