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 $58.79   7.783%   $63.3656   $63.37   $63.35   $63.40  
  Purchase #2 $103.93   6.233%   $110.408   $110.41   $110.40   $110.40  
  Purchase #3 $79.43   3.453%   $82.1727   $82.17   $82.15   $82.20  
  Purchase #4 $63.96   6.409%   $68.0592   $68.06   $68.05   $68.10  
  Purchase #5 $240.73   10.609%   $266.269   $266.27   $266.25   $266.30  
  Purchase #6 $175.75   7.388%   $188.7344   $188.73   $188.75   $188.70  
  Purchase #7 $250.84   12.322%   $281.7485   $281.75   $281.75   $281.70  
  7 purchase totals = $973.43       $1,060.7574   $1,060.76   $1,060.70   $1,060.80