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	$66.81	7.117%	$71.5649	$71.56	$71.55	$71.60
Purchase #2	$140.30	12.243%	$157.4769	$157.48	$157.50	$157.50
Purchase #3	$151.44	7.168%	$162.2952	$162.30	$162.30	$162.30
Purchase #4	$121.85	12.697%	$137.3213	$137.32	$137.30	$137.30
Purchase #5	$161.92	9.774%	$177.7461	$177.75	$177.75	$177.70
Purchase #6	$115.67	3.123%	$119.2824	$119.28	$119.30	$119.30
Purchase #7	$168.79	10.138%	$185.9019	$185.90	$185.90	$185.90
7 purchase totals =	$926.78		$1,011.5887	$1,011.59	$1,011.60	$1,011.60