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 $89.37   5.240%   $94.053   $94.05   $94.05   $94.10  
  Purchase #2 $204.46   11.619%   $228.2162   $228.22   $228.20   $228.20  
  Purchase #3 $209.91   13.358%   $237.9498   $237.95   $237.95   $237.90  
  Purchase #4 $56.32   3.287%   $58.1712   $58.17   $58.15   $58.20  
  Purchase #5 $62.95   9.817%   $69.1298   $69.13   $69.15   $69.10  
  Purchase #6 $180.68   13.705%   $205.4422   $205.44   $205.45   $205.40  
  Purchase #7 $213.46   6.321%   $226.9528   $226.95   $226.95   $227.00  
  7 purchase totals = $1,017.15       $1,119.9150   $1,119.91   $1,119.90   $1,119.90