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	$155.78	7.378%	$167.2734	$167.27	$167.25	$167.30
Purchase #2	$227.49	8.342%	$246.4672	$246.47	$246.45	$246.50
Purchase #3	$145.78	11.539%	$162.6016	$162.60	$162.60	$162.60
Purchase #4	$139.98	12.126%	$156.954	$156.95	$156.95	$157.00
Purchase #5	$10.91	5.191%	$11.4763	$11.48	$11.50	$11.50
Purchase #6	$168.94	8.621%	$183.5043	$183.50	$183.50	$183.50
Purchase #7	$221.69	6.861%	$236.9002	$236.90	$236.90	$236.90
7 purchase totals =	$1,070.57		$1,165.1770	$1,165.17	$1,165.15	$1,165.30