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	$149.49	10.591%	$165.3225	$165.32	$165.30	$165.30
Purchase #2	$33.75	6.579%	$35.9704	$35.97	$35.95	$36.00
Purchase #3	$98.42	5.135%	$103.4739	$103.47	$103.45	$103.50
Purchase #4	$170.76	11.767%	$190.8533	$190.85	$190.85	$190.90
Purchase #5	$123.89	13.688%	$140.8481	$140.85	$140.85	$140.80
Purchase #6	$139.78	7.757%	$150.6227	$150.62	$150.60	$150.60
Purchase #7	$166.46	7.246%	$178.5217	$178.52	$178.50	$178.50
7 purchase totals =	$882.55		$965.6126	$965.60	$965.50	$965.60