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 $211.83   10.707%   $234.5106   $234.51   $234.50   $234.50  
  Purchase #2 $186.51   5.832%   $197.3873   $197.39   $197.40   $197.40  
  Purchase #3 $79.50   7.847%   $85.7384   $85.74   $85.75   $85.70  
  Purchase #4 $57.37   6.172%   $60.9109   $60.91   $60.90   $60.90  
  Purchase #5 $83.58   13.526%   $94.885   $94.89   $94.90   $94.90  
  Purchase #6 $184.28   10.659%   $203.9224   $203.92   $203.90   $203.90  
  Purchase #7 $63.75   10.869%   $70.679   $70.68   $70.70   $70.70  
  7 purchase totals = $866.82       $948.0336   $948.04   $948.05   $948.00