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 $69.51   6.397%   $73.9566   $73.96   $73.95   $74.00  
  Purchase #2 $162.78   11.632%   $181.7146   $181.71   $181.70   $181.70  
  Purchase #3 $30.29   9.500%   $33.1676   $33.17   $33.15   $33.20  
  Purchase #4 $126.61   8.509%   $137.3832   $137.38   $137.40   $137.40  
  Purchase #5 $236.69   3.820%   $245.7316   $245.73   $245.75   $245.70  
  Purchase #6 $232.51   6.102%   $246.6978   $246.70   $246.70   $246.70  
  Purchase #7 $100.37   12.459%   $112.8751   $112.88   $112.90   $112.90  
  7 purchase totals = $958.76       $1,031.5265   $1,031.53   $1,031.55   $1,031.60