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 $174.34   11.693%   $194.7256   $194.73   $194.75   $194.70  
  Purchase #2 $147.63   3.254%   $152.4339   $152.43   $152.45   $152.40  
  Purchase #3 $190.29   7.822%   $205.1745   $205.17   $205.15   $205.20  
  Purchase #4 $55.46   6.220%   $58.9096   $58.91   $58.90   $58.90  
  Purchase #5 $66.68   5.583%   $70.4027   $70.40   $70.40   $70.40  
  Purchase #6 $146.98   5.288%   $154.7523   $154.75   $154.75   $154.80  
  Purchase #7 $177.30   6.566%   $188.9415   $188.94   $188.95   $188.90  
  7 purchase totals = $958.68       $1,025.3401   $1,025.33   $1,025.35   $1,025.30