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 $67.37   8.452%   $73.0641   $73.06   $73.05   $73.10  
  Purchase #2 $195.61   6.215%   $207.7672   $207.77   $207.75   $207.80  
  Purchase #3 $120.76   8.665%   $131.2239   $131.22   $131.20   $131.20  
  Purchase #4 $203.36   8.427%   $220.4971   $220.50   $220.50   $220.50  
  Purchase #5 $69.31   7.374%   $74.4209   $74.42   $74.40   $74.40  
  Purchase #6 $204.80   11.284%   $227.9096   $227.91   $227.90   $227.90  
  Purchase #7 $238.48   9.315%   $260.6944   $260.69   $260.70   $260.70  
  7 purchase totals = $1,099.69       $1,195.5772   $1,195.57   $1,195.50   $1,195.60