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 $87.45   8.661%   $95.024   $95.02   $95.00   $95.00  
  Purchase #2 $222.39   11.323%   $247.5712   $247.57   $247.55   $247.60  
  Purchase #3 $84.90   4.475%   $88.6993   $88.70   $88.70   $88.70  
  Purchase #4 $92.95   11.387%   $103.5342   $103.53   $103.55   $103.50  
  Purchase #5 $65.68   5.256%   $69.1321   $69.13   $69.15   $69.10  
  Purchase #6 $187.71   5.760%   $198.5221   $198.52   $198.50   $198.50  
  Purchase #7 $195.98   5.193%   $206.1572   $206.16   $206.15   $206.20  
  7 purchase totals = $937.06       $1,008.6401   $1,008.63   $1,008.60   $1,008.60