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 $86.32   7.525%   $92.8156   $92.82   $92.80   $92.80  
  Purchase #2 $31.25   7.552%   $33.61   $33.61   $33.60   $33.60  
  Purchase #3 $247.38   11.562%   $275.9821   $275.98   $276.00   $276.00  
  Purchase #4 $81.58   4.254%   $85.0504   $85.05   $85.05   $85.10  
  Purchase #5 $188.75   9.745%   $207.1437   $207.14   $207.15   $207.10  
  Purchase #6 $215.48   5.650%   $227.6546   $227.65   $227.65   $227.70  
  Purchase #7 $232.51   4.800%   $243.6705   $243.67   $243.65   $243.70  
  7 purchase totals = $1,083.27       $1,165.9269   $1,165.92   $1,165.90   $1,166.00