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	$156.54	13.766%	$178.0893	$178.09	$178.10	$178.10
Purchase #2	$78.94	11.383%	$87.9257	$87.93	$87.95	$87.90
Purchase #3	$53.28	11.605%	$59.4631	$59.46	$59.45	$59.50
Purchase #4	$175.98	11.591%	$196.3778	$196.38	$196.40	$196.40
Purchase #5	$226.69	7.408%	$243.4832	$243.48	$243.50	$243.50
Purchase #6	$122.99	5.803%	$130.1271	$130.13	$130.15	$130.10
Purchase #7	$19.26	11.468%	$21.4687	$21.47	$21.45	$21.50
7 purchase totals =	$833.68		$916.9349	$916.94	$917.00	$917.00