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 $69.41   4.750%   $72.707   $72.71   $72.70   $72.70  
  Purchase #2 $219.50   12.608%   $247.1746   $247.17   $247.15   $247.20  
  Purchase #3 $246.66   4.516%   $257.7992   $257.80   $257.80   $257.80  
  Purchase #4 $191.82   13.463%   $217.6447   $217.64   $217.65   $217.60  
  Purchase #5 $249.62   5.651%   $263.726   $263.73   $263.75   $263.70  
  Purchase #6 $213.93   8.399%   $231.898   $231.90   $231.90   $231.90  
  Purchase #7 $182.39   6.326%   $193.928   $193.93   $193.95   $193.90  
  7 purchase totals = $1,373.33       $1,484.8775   $1,484.88   $1,484.90   $1,484.80