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	$49.34	5.182%	$51.8968	$51.90	$51.90	$51.90
Purchase #2	$207.61	4.499%	$216.9504	$216.95	$216.95	$217.00
Purchase #3	$132.48	12.107%	$148.5194	$148.52	$148.50	$148.50
Purchase #4	$40.93	3.753%	$42.4661	$42.47	$42.45	$42.50
Purchase #5	$64.31	11.509%	$71.7114	$71.71	$71.70	$71.70
Purchase #6	$117.89	6.485%	$125.5352	$125.54	$125.55	$125.50
Purchase #7	$148.44	11.791%	$165.9426	$165.94	$165.95	$165.90
7 purchase totals =	$761.00		$823.0219	$823.03	$823.00	$823.00