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	$92.90	13.750%	$105.6738	$105.67	$105.65	$105.70
Purchase #2	$56.37	5.268%	$59.3396	$59.34	$59.35	$59.30
Purchase #3	$250.83	12.135%	$281.2682	$281.27	$281.25	$281.30
Purchase #4	$30.56	4.568%	$31.956	$31.96	$31.95	$32.00
Purchase #5	$203.76	5.397%	$214.7569	$214.76	$214.75	$214.80
Purchase #6	$40.91	9.759%	$44.9024	$44.90	$44.90	$44.90
Purchase #7	$136.84	13.142%	$154.8235	$154.82	$154.80	$154.80
7 purchase totals =	$812.17		$892.7204	$892.72	$892.65	$892.80