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	$52.58	13.460%	$59.6573	$59.66	$59.65	$59.70
Purchase #2	$6.68	11.524%	$7.4498	$7.45	$7.45	$7.40
Purchase #3	$83.35	8.114%	$90.113	$90.11	$90.10	$90.10
Purchase #4	$213.62	8.326%	$231.406	$231.41	$231.40	$231.40
Purchase #5	$227.56	9.519%	$249.2214	$249.22	$249.20	$249.20
Purchase #6	$86.60	9.571%	$94.8885	$94.89	$94.90	$94.90
Purchase #7	$227.52	12.184%	$255.241	$255.24	$255.25	$255.20
7 purchase totals =	$897.91		$987.9770	$987.98	$987.95	$987.90