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 $179.84   8.751%   $195.5778   $195.58   $195.60   $195.60  
  Purchase #2 $44.81   4.559%   $46.8529   $46.85   $46.85   $46.90  
  Purchase #3 $144.82   10.616%   $160.1941   $160.19   $160.20   $160.20  
  Purchase #4 $228.98   10.856%   $253.8381   $253.84   $253.85   $253.80  
  Purchase #5 $157.85   8.686%   $171.5609   $171.56   $171.55   $171.60  
  Purchase #6 $166.54   9.662%   $182.6311   $182.63   $182.65   $182.60  
  Purchase #7 $14.90   13.463%   $16.906   $16.91   $16.90   $16.90  
  7 purchase totals = $937.74       $1,027.5609   $1,027.56   $1,027.60   $1,027.60