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 $33.31   5.872%   $35.266   $35.27   $35.25   $35.30  
  Purchase #2 $213.88   11.168%   $237.7661   $237.77   $237.75   $237.80  
  Purchase #3 $94.46   6.170%   $100.2882   $100.29   $100.30   $100.30  
  Purchase #4 $150.88   6.655%   $160.9211   $160.92   $160.90   $160.90  
  Purchase #5 $9.82   3.259%   $10.14   $10.14   $10.15   $10.10  
  Purchase #6 $195.41   12.462%   $219.762   $219.76   $219.75   $219.80  
  Purchase #7 $245.45   12.418%   $275.93   $275.93   $275.95   $275.90  
  7 purchase totals = $943.21       $1,040.0734   $1,040.08   $1,040.05   $1,040.10