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	$105.25	8.214%	$113.8952	$113.90	$113.90	$113.90
Purchase #2	$51.37	11.162%	$57.1039	$57.10	$57.10	$57.10
Purchase #3	$88.89	6.603%	$94.7594	$94.76	$94.75	$94.80
Purchase #4	$225.25	11.250%	$250.5906	$250.59	$250.60	$250.60
Purchase #5	$85.78	11.417%	$95.5735	$95.57	$95.55	$95.60
Purchase #6	$240.54	6.872%	$257.0699	$257.07	$257.05	$257.10
Purchase #7	$69.58	4.618%	$72.7932	$72.79	$72.80	$72.80
7 purchase totals =	$866.66		$941.7857	$941.78	$941.75	$941.90