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 $112.31   5.693%   $118.7038   $118.70   $118.70   $118.70  
  Purchase #2 $73.62   12.303%   $82.6775   $82.68   $82.70   $82.70  
  Purchase #3 $95.95   4.378%   $100.1507   $100.15   $100.15   $100.20  
  Purchase #4 $209.63   11.274%   $233.2637   $233.26   $233.25   $233.30  
  Purchase #5 $231.91   13.708%   $263.7002   $263.70   $263.70   $263.70  
  Purchase #6 $245.96   4.855%   $257.9014   $257.90   $257.90   $257.90  
  Purchase #7 $25.46   7.231%   $27.301   $27.30   $27.30   $27.30  
  7 purchase totals = $994.84       $1,083.6983   $1,083.69   $1,083.70   $1,083.80