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 $124.70   7.811%   $134.4403   $134.44   $134.45   $134.40  
  Purchase #2 $158.50   9.556%   $173.6463   $173.65   $173.65   $173.60  
  Purchase #3 $236.43   10.775%   $261.9053   $261.91   $261.90   $261.90  
  Purchase #4 $105.46   10.764%   $116.8117   $116.81   $116.80   $116.80  
  Purchase #5 $112.87   4.180%   $117.588   $117.59   $117.60   $117.60  
  Purchase #6 $50.93   3.747%   $52.8383   $52.84   $52.85   $52.80  
  Purchase #7 $185.79   5.463%   $195.9397   $195.94   $195.95   $195.90  
  7 purchase totals = $974.68       $1,053.1696   $1,053.18   $1,053.20   $1,053.00