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	$103.62	10.193%	$114.182	$114.18	$114.20	$114.20
Purchase #2	$220.98	9.777%	$242.5852	$242.59	$242.60	$242.60
Purchase #3	$97.89	8.300%	$106.0149	$106.01	$106.00	$106.00
Purchase #4	$79.94	12.392%	$89.8462	$89.85	$89.85	$89.80
Purchase #5	$140.71	11.184%	$156.447	$156.45	$156.45	$156.40
Purchase #6	$113.59	10.328%	$125.3216	$125.32	$125.30	$125.30
Purchase #7	$19.85	10.372%	$21.9088	$21.91	$21.90	$21.90
7 purchase totals =	$776.58		$856.3057	$856.31	$856.30	$856.20