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	$82.80	3.693%	$85.8578	$85.86	$85.85	$85.90
Purchase #2	$190.41	12.802%	$214.7863	$214.79	$214.80	$214.80
Purchase #3	$44.86	11.103%	$49.8408	$49.84	$49.85	$49.80
Purchase #4	$25.73	5.573%	$27.1639	$27.16	$27.15	$27.20
Purchase #5	$196.72	3.363%	$203.3357	$203.34	$203.35	$203.30
Purchase #6	$242.60	13.624%	$275.6518	$275.65	$275.65	$275.70
Purchase #7	$42.41	7.402%	$45.5492	$45.55	$45.55	$45.50
7 purchase totals =	$825.53		$902.1855	$902.19	$902.20	$902.20