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 $43.41   10.470%   $47.955   $47.96   $47.95   $48.00  
  Purchase #2 $202.72   13.237%   $229.554   $229.55   $229.55   $229.60  
  Purchase #3 $105.96   12.371%   $119.0683   $119.07   $119.05   $119.10  
  Purchase #4 $44.37   3.805%   $46.0583   $46.06   $46.05   $46.10  
  Purchase #5 $230.35   12.436%   $258.9963   $259.00   $259.00   $259.00  
  Purchase #6 $204.96   12.431%   $230.4386   $230.44   $230.45   $230.40  
  Purchase #7 $78.35   12.555%   $88.1868   $88.19   $88.20   $88.20  
  7 purchase totals = $910.12       $1,020.2573   $1,020.27   $1,020.25   $1,020.40