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	$87.83	8.808%	$95.5661	$95.57	$95.55	$95.60
Purchase #2	$72.77	4.777%	$76.2462	$76.25	$76.25	$76.20
Purchase #3	$165.71	11.406%	$184.6109	$184.61	$184.60	$184.60
Purchase #4	$116.47	9.711%	$127.7804	$127.78	$127.80	$127.80
Purchase #5	$162.54	12.593%	$183.0087	$183.01	$183.00	$183.00
Purchase #6	$150.53	3.723%	$156.1342	$156.13	$156.15	$156.10
Purchase #7	$185.95	4.826%	$194.9239	$194.92	$194.90	$194.90
7 purchase totals =	$941.80		$1,018.2704	$1,018.27	$1,018.25	$1,018.20