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 $93.71   5.245%   $98.6251   $98.63   $98.65   $98.60  
  Purchase #2 $235.46   6.419%   $250.5742   $250.57   $250.55   $250.60  
  Purchase #3 $180.36   4.117%   $187.7854   $187.79   $187.80   $187.80  
  Purchase #4 $243.82   5.261%   $256.6474   $256.65   $256.65   $256.60  
  Purchase #5 $25.52   8.853%   $27.7793   $27.78   $27.80   $27.80  
  Purchase #6 $190.81   8.158%   $206.3763   $206.38   $206.40   $206.40  
  Purchase #7 $186.62   5.786%   $197.4178   $197.42   $197.40   $197.40  
  7 purchase totals = $1,156.30       $1,225.2055   $1,225.22   $1,225.25   $1,225.20