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 $49.37   6.849%   $52.7514   $52.75   $52.75   $52.80  
  Purchase #2 $193.69   8.572%   $210.2931   $210.29   $210.30   $210.30  
  Purchase #3 $207.95   11.432%   $231.7228   $231.72   $231.70   $231.70  
  Purchase #4 $237.67   11.361%   $264.6717   $264.67   $264.65   $264.70  
  Purchase #5 $132.84   7.360%   $142.617   $142.62   $142.60   $142.60  
  Purchase #6 $127.61   9.840%   $140.1668   $140.17   $140.15   $140.20  
  Purchase #7 $5.90   13.734%   $6.7103   $6.71   $6.70   $6.70  
  7 purchase totals = $955.03       $1,048.9331   $1,048.93   $1,048.85   $1,049.00