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	$95.90	13.422%	$108.7717	$108.77	$108.75	$108.80
Purchase #2	$84.92	13.465%	$96.3545	$96.35	$96.35	$96.40
Purchase #3	$60.60	10.422%	$66.9157	$66.92	$66.90	$66.90
Purchase #4	$150.47	5.598%	$158.8933	$158.89	$158.90	$158.90
Purchase #5	$54.70	8.554%	$59.379	$59.38	$59.40	$59.40
Purchase #6	$35.38	4.531%	$36.9831	$36.98	$37.00	$37.00
Purchase #7	$216.57	8.541%	$235.0672	$235.07	$235.05	$235.10
7 purchase totals =	$698.54		$762.3645	$762.36	$762.35	$762.50