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 $236.99   7.303%   $254.2974   $254.30   $254.30   $254.30  
  Purchase #2 $69.76   9.224%   $76.1947   $76.19   $76.20   $76.20  
  Purchase #3 $169.64   5.520%   $179.0041   $179.00   $179.00   $179.00  
  Purchase #4 $203.62   6.562%   $216.9815   $216.98   $217.00   $217.00  
  Purchase #5 $87.72   4.753%   $91.8893   $91.89   $91.90   $91.90  
  Purchase #6 $182.40   10.412%   $201.3915   $201.39   $201.40   $201.40  
  Purchase #7 $167.99   13.815%   $191.1978   $191.20   $191.20   $191.20  
  7 purchase totals = $1,118.12       $1,210.9563   $1,210.95   $1,211.00   $1,211.00