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	$144.79	4.745%	$151.6603	$151.66	$151.65	$151.70
Purchase #2	$116.85	7.839%	$126.0099	$126.01	$126.00	$126.00
Purchase #3	$125.79	13.287%	$142.5037	$142.50	$142.50	$142.50
Purchase #4	$247.32	11.295%	$275.2548	$275.25	$275.25	$275.30
Purchase #5	$141.81	7.585%	$152.5663	$152.57	$152.55	$152.60
Purchase #6	$199.71	9.536%	$218.7543	$218.75	$218.75	$218.80
Purchase #7	$220.78	3.223%	$227.8957	$227.90	$227.90	$227.90
7 purchase totals =	$1,197.05		$1,294.6450	$1,294.64	$1,294.60	$1,294.80