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 $219.25   12.535%   $246.733   $246.73   $246.75   $246.70  
  Purchase #2 $146.27   3.528%   $151.4304   $151.43   $151.45   $151.40  
  Purchase #3 $189.85   5.304%   $199.9196   $199.92   $199.90   $199.90  
  Purchase #4 $35.64   10.606%   $39.42   $39.42   $39.40   $39.40  
  Purchase #5 $207.70   6.155%   $220.4839   $220.48   $220.50   $220.50  
  Purchase #6 $216.38   4.274%   $225.6281   $225.63   $225.65   $225.60  
  Purchase #7 $48.86   3.400%   $50.5212   $50.52   $50.50   $50.50  
  7 purchase totals = $1,063.95       $1,134.1362   $1,134.13   $1,134.15   $1,134.00