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 $204.93   5.307%   $215.8056   $215.81   $215.80   $215.80  
  Purchase #2 $218.77   3.297%   $225.9828   $225.98   $226.00   $226.00  
  Purchase #3 $23.67   13.384%   $26.838   $26.84   $26.85   $26.80  
  Purchase #4 $114.56   6.456%   $121.956   $121.96   $121.95   $122.00  
  Purchase #5 $116.44   13.396%   $132.0383   $132.04   $132.05   $132.00  
  Purchase #6 $146.82   7.826%   $158.3101   $158.31   $158.30   $158.30  
  Purchase #7 $131.86   9.402%   $144.2575   $144.26   $144.25   $144.30  
  7 purchase totals = $957.05       $1,025.1883   $1,025.20   $1,025.20   $1,025.20