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 $180.89   9.269%   $197.6567   $197.66   $197.65   $197.70  
  Purchase #2 $87.57   10.607%   $96.8585   $96.86   $96.85   $96.90  
  Purchase #3 $201.47   4.730%   $210.9995   $211.00   $211.00   $211.00  
  Purchase #4 $63.68   12.435%   $71.5986   $71.60   $71.60   $71.60  
  Purchase #5 $113.94   3.515%   $117.945   $117.95   $117.95   $117.90  
  Purchase #6 $39.90   4.474%   $41.6851   $41.69   $41.70   $41.70  
  Purchase #7 $60.71   11.494%   $67.688   $67.69   $67.70   $67.70  
  7 purchase totals = $748.16       $804.4314   $804.45   $804.45   $804.50