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 $67.59   8.206%   $73.1364   $73.14   $73.15   $73.10  
  Purchase #2 $169.81   10.582%   $187.7793   $187.78   $187.80   $187.80  
  Purchase #3 $46.37   13.635%   $52.6925   $52.69   $52.70   $52.70  
  Purchase #4 $68.85   10.548%   $76.1123   $76.11   $76.10   $76.10  
  Purchase #5 $137.57   8.799%   $149.6748   $149.67   $149.65   $149.70  
  Purchase #6 $88.89   10.600%   $98.3123   $98.31   $98.30   $98.30  
  Purchase #7 $168.96   7.444%   $181.5374   $181.54   $181.55   $181.50  
  7 purchase totals = $748.04       $819.2450   $819.24   $819.25   $819.20