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 $176.92   3.185%   $182.5549   $182.55   $182.55   $182.60  
  Purchase #2 $236.53   4.396%   $246.9279   $246.93   $246.95   $246.90  
  Purchase #3 $210.75   12.524%   $237.1443   $237.14   $237.15   $237.10  
  Purchase #4 $80.58   5.120%   $84.7057   $84.71   $84.70   $84.70  
  Purchase #5 $204.51   8.472%   $221.8361   $221.84   $221.85   $221.80  
  Purchase #6 $128.31   3.112%   $132.303   $132.30   $132.30   $132.30  
  Purchase #7 $58.41   5.151%   $61.4187   $61.42   $61.40   $61.40  
  7 purchase totals = $1,096.01       $1,166.8906   $1,166.89   $1,166.90   $1,166.80