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	$53.38	11.506%	$59.5219	$59.52	$59.50	$59.50
Purchase #2	$71.77	8.548%	$77.9049	$77.90	$77.90	$77.90
Purchase #3	$37.55	9.417%	$41.0861	$41.09	$41.10	$41.10
Purchase #4	$29.41	12.767%	$33.1648	$33.16	$33.15	$33.20
Purchase #5	$180.27	3.389%	$186.3794	$186.38	$186.40	$186.40
Purchase #6	$185.58	8.537%	$201.423	$201.42	$201.40	$201.40
Purchase #7	$6.75	12.353%	$7.5838	$7.58	$7.60	$7.60
7 purchase totals =	$564.71		$607.0639	$607.05	$607.05	$607.10