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	$53.65	10.845%	$59.4683	$59.47	$59.45	$59.50
Purchase #2	$125.95	4.770%	$131.9578	$131.96	$131.95	$132.00
Purchase #3	$27.65	6.864%	$29.5479	$29.55	$29.55	$29.50
Purchase #4	$6.86	12.454%	$7.7143	$7.71	$7.70	$7.70
Purchase #5	$159.52	10.799%	$176.7466	$176.75	$176.75	$176.70
Purchase #6	$73.90	13.598%	$83.9489	$83.95	$83.95	$83.90
Purchase #7	$176.55	5.342%	$185.9813	$185.98	$186.00	$186.00
7 purchase totals =	$624.08		$675.3651	$675.37	$675.35	$675.30