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	$116.29	13.421%	$131.8973	$131.90	$131.90	$131.90
Purchase #2	$109.91	8.815%	$119.5986	$119.60	$119.60	$119.60
Purchase #3	$30.64	3.504%	$31.7136	$31.71	$31.70	$31.70
Purchase #4	$152.38	5.314%	$160.4775	$160.48	$160.50	$160.50
Purchase #5	$106.31	3.162%	$109.6715	$109.67	$109.65	$109.70
Purchase #6	$40.53	5.558%	$42.7827	$42.78	$42.80	$42.80
Purchase #7	$126.76	10.823%	$140.4792	$140.48	$140.50	$140.50
7 purchase totals =	$682.82		$736.6204	$736.62	$736.65	$736.70