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	$91.45	10.373%	$100.9361	$100.94	$100.95	$100.90
Purchase #2	$33.37	11.159%	$37.0938	$37.09	$37.10	$37.10
Purchase #3	$28.59	12.310%	$32.1094	$32.11	$32.10	$32.10
Purchase #4	$196.66	5.650%	$207.7713	$207.77	$207.75	$207.80
Purchase #5	$159.76	4.509%	$166.9636	$166.96	$166.95	$167.00
Purchase #6	$160.88	10.316%	$177.4764	$177.48	$177.50	$177.50
Purchase #7	$163.87	9.545%	$179.5114	$179.51	$179.50	$179.50
7 purchase totals =	$834.58		$901.8620	$901.86	$901.85	$901.90