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 $200.94   5.490%   $211.9716   $211.97   $211.95   $212.00  
  Purchase #2 $237.54   5.326%   $250.1914   $250.19   $250.20   $250.20  
  Purchase #3 $125.62   5.673%   $132.7464   $132.75   $132.75   $132.70  
  Purchase #4 $26.28   11.369%   $29.2678   $29.27   $29.25   $29.30  
  Purchase #5 $84.64   9.716%   $92.8636   $92.86   $92.85   $92.90  
  Purchase #6 $247.25   4.663%   $258.7793   $258.78   $258.80   $258.80  
  Purchase #7 $64.45   13.211%   $72.9645   $72.96   $72.95   $73.00  
  7 purchase totals = $986.72       $1,048.7846   $1,048.78   $1,048.75   $1,048.90