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	$75.78	3.541%	$78.4634	$78.46	$78.45	$78.50
Purchase #2	$11.99	5.398%	$12.6372	$12.64	$12.65	$12.60
Purchase #3	$175.87	11.410%	$195.9368	$195.94	$195.95	$195.90
Purchase #4	$93.97	4.296%	$98.007	$98.01	$98.00	$98.00
Purchase #5	$24.47	11.772%	$27.3506	$27.35	$27.35	$27.40
Purchase #6	$34.42	5.672%	$36.3723	$36.37	$36.35	$36.40
Purchase #7	$55.65	11.663%	$62.1405	$62.14	$62.15	$62.10
7 purchase totals =	$472.15		$510.9078	$510.91	$510.90	$510.90