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	$218.25	4.870%	$228.8788	$228.88	$228.90	$228.90
Purchase #2	$77.51	10.751%	$85.8431	$85.84	$85.85	$85.80
Purchase #3	$76.30	13.643%	$86.7096	$86.71	$86.70	$86.70
Purchase #4	$89.93	6.314%	$95.6082	$95.61	$95.60	$95.60
Purchase #5	$32.57	8.660%	$35.3906	$35.39	$35.40	$35.40
Purchase #6	$108.89	3.405%	$112.5977	$112.60	$112.60	$112.60
Purchase #7	$113.94	9.171%	$124.3894	$124.39	$124.40	$124.40
7 purchase totals =	$717.39		$769.4174	$769.42	$769.45	$769.40