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 $58.85   6.452%   $62.647   $62.65   $62.65   $62.60  
  Purchase #2 $127.90   7.404%   $137.3697   $137.37   $137.35   $137.40  
  Purchase #3 $187.79   13.333%   $212.828   $212.83   $212.85   $212.80  
  Purchase #4 $222.63   4.651%   $232.9845   $232.98   $233.00   $233.00  
  Purchase #5 $52.60   5.806%   $55.654   $55.65   $55.65   $55.70  
  Purchase #6 $213.62   10.869%   $236.8384   $236.84   $236.85   $236.80  
  Purchase #7 $78.54   5.423%   $82.7992   $82.80   $82.80   $82.80  
  7 purchase totals = $941.93       $1,021.1208   $1,021.12   $1,021.15   $1,021.10