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 $195.82   11.163%   $217.6794   $217.68   $217.70   $217.70  
  Purchase #2 $56.31   4.391%   $58.7826   $58.78   $58.80   $58.80  
  Purchase #3 $177.85   8.783%   $193.4706   $193.47   $193.45   $193.50  
  Purchase #4 $153.87   5.264%   $161.9697   $161.97   $161.95   $162.00  
  Purchase #5 $110.99   5.785%   $117.4108   $117.41   $117.40   $117.40  
  Purchase #6 $19.84   11.464%   $22.1145   $22.11   $22.10   $22.10  
  Purchase #7 $165.63   9.201%   $180.8696   $180.87   $180.85   $180.90  
  7 purchase totals = $880.31       $952.2972   $952.29   $952.25   $952.40