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 $60.64   13.798%   $69.0071   $69.01   $69.00   $69.00  
  Purchase #2 $231.68   8.609%   $251.6253   $251.63   $251.65   $251.60  
  Purchase #3 $59.33   5.388%   $62.5267   $62.53   $62.55   $62.50  
  Purchase #4 $82.86   3.668%   $85.8993   $85.90   $85.90   $85.90  
  Purchase #5 $195.77   5.250%   $206.0479   $206.05   $206.05   $206.00  
  Purchase #6 $210.62   8.590%   $228.7123   $228.71   $228.70   $228.70  
  Purchase #7 $247.51   4.121%   $257.7099   $257.71   $257.70   $257.70  
  7 purchase totals = $1,088.41       $1,161.5285   $1,161.54   $1,161.55   $1,161.40