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 $184.97   10.640%   $204.6508   $204.65   $204.65   $204.70  
  Purchase #2 $59.36   12.811%   $66.9646   $66.96   $66.95   $67.00  
  Purchase #3 $60.65   3.384%   $62.7024   $62.70   $62.70   $62.70  
  Purchase #4 $62.46   3.134%   $64.4175   $64.42   $64.40   $64.40  
  Purchase #5 $190.38   6.209%   $202.2007   $202.20   $202.20   $202.20  
  Purchase #6 $241.75   8.819%   $263.0699   $263.07   $263.05   $263.10  
  Purchase #7 $28.25   12.646%   $31.8225   $31.82   $31.80   $31.80  
  7 purchase totals = $827.82       $895.8284   $895.82   $895.75   $895.90