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 $212.81   11.697%   $237.7024   $237.70   $237.70   $237.70  
  Purchase #2 $84.63   4.266%   $88.2403   $88.24   $88.25   $88.20  
  Purchase #3 $115.56   8.612%   $125.512   $125.51   $125.50   $125.50  
  Purchase #4 $97.31   5.338%   $102.5044   $102.50   $102.50   $102.50  
  Purchase #5 $130.93   13.538%   $148.6553   $148.66   $148.65   $148.70  
  Purchase #6 $137.35   7.246%   $147.3024   $147.30   $147.30   $147.30  
  Purchase #7 $200.30   4.644%   $209.6019   $209.60   $209.60   $209.60  
  7 purchase totals = $978.89       $1,059.5187   $1,059.51   $1,059.50   $1,059.50