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 $58.26   4.541%   $60.9056   $60.91   $60.90   $60.90  
  Purchase #2 $114.95   8.140%   $124.3069   $124.31   $124.30   $124.30  
  Purchase #3 $8.72   12.210%   $9.7847   $9.78   $9.80   $9.80  
  Purchase #4 $24.58   6.417%   $26.1573   $26.16   $26.15   $26.20  
  Purchase #5 $159.25   13.870%   $181.338   $181.34   $181.35   $181.30  
  Purchase #6 $219.39   6.368%   $233.3608   $233.36   $233.35   $233.40  
  Purchase #7 $15.67   6.599%   $16.7041   $16.70   $16.70   $16.70  
  7 purchase totals = $600.82       $652.5574   $652.56   $652.55   $652.60