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 $44.95   6.152%   $47.7153   $47.72   $47.70   $47.70  
  Purchase #2 $6.56   8.596%   $7.1239   $7.12   $7.10   $7.10  
  Purchase #3 $228.89   5.367%   $241.1745   $241.17   $241.15   $241.20  
  Purchase #4 $186.93   12.739%   $210.743   $210.74   $210.75   $210.70  
  Purchase #5 $159.84   13.267%   $181.046   $181.05   $181.05   $181.00  
  Purchase #6 $64.90   8.280%   $70.2737   $70.27   $70.25   $70.30  
  Purchase #7 $238.88   11.406%   $266.1267   $266.13   $266.15   $266.10  
  7 purchase totals = $930.95       $1,024.2031   $1,024.20   $1,024.15   $1,024.10