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 $113.77   8.417%   $123.346   $123.35   $123.35   $123.30  
  Purchase #2 $146.88   12.611%   $165.403   $165.40   $165.40   $165.40  
  Purchase #3 $117.79   13.724%   $133.9555   $133.96   $133.95   $134.00  
  Purchase #4 $181.93   6.672%   $194.0684   $194.07   $194.05   $194.10  
  Purchase #5 $227.93   6.829%   $243.4953   $243.50   $243.50   $243.50  
  Purchase #6 $134.75   11.208%   $149.8528   $149.85   $149.85   $149.90  
  Purchase #7 $130.70   9.327%   $142.8904   $142.89   $142.90   $142.90  
  7 purchase totals = $1,053.75       $1,153.0114   $1,153.02   $1,153.00   $1,153.10