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 $84.76   13.143%   $95.9   $95.90   $95.90   $95.90  
  Purchase #2 $219.75   3.562%   $227.5775   $227.58   $227.60   $227.60  
  Purchase #3 $128.84   13.455%   $146.1754   $146.18   $146.20   $146.20  
  Purchase #4 $49.53   6.789%   $52.8926   $52.89   $52.90   $52.90  
  Purchase #5 $215.32   3.666%   $223.2136   $223.21   $223.20   $223.20  
  Purchase #6 $192.60   12.638%   $216.9408   $216.94   $216.95   $216.90  
  Purchase #7 $163.27   3.798%   $169.471   $169.47   $169.45   $169.50  
  7 purchase totals = $1,054.07       $1,132.1709   $1,132.17   $1,132.20   $1,132.20