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	$83.98	3.179%	$86.6497	$86.65	$86.65	$86.60
Purchase #2	$81.55	3.751%	$84.6089	$84.61	$84.60	$84.60
Purchase #3	$139.69	12.654%	$157.3664	$157.37	$157.35	$157.40
Purchase #4	$30.84	4.214%	$32.1396	$32.14	$32.15	$32.10
Purchase #5	$162.33	10.800%	$179.8616	$179.86	$179.85	$179.90
Purchase #6	$34.54	8.701%	$37.5453	$37.55	$37.55	$37.50
Purchase #7	$134.77	5.155%	$141.7174	$141.72	$141.70	$141.70
7 purchase totals =	$667.70		$719.8889	$719.90	$719.85	$719.80