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 $84.87   12.115%   $95.152   $95.15   $95.15   $95.20  
  Purchase #2 $62.40   8.185%   $67.5074   $67.51   $67.50   $67.50  
  Purchase #3 $196.80   5.649%   $207.9172   $207.92   $207.90   $207.90  
  Purchase #4 $139.79   6.855%   $149.3726   $149.37   $149.35   $149.40  
  Purchase #5 $43.63   12.703%   $49.1723   $49.17   $49.15   $49.20  
  Purchase #6 $245.98   12.504%   $276.7373   $276.74   $276.75   $276.70  
  Purchase #7 $163.93   7.552%   $176.31   $176.31   $176.30   $176.30  
  7 purchase totals = $937.40       $1,022.1688   $1,022.17   $1,022.10   $1,022.20