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 $87.97   5.282%   $92.6166   $92.62   $92.60   $92.60  
  Purchase #2 $197.65   8.643%   $214.7329   $214.73   $214.75   $214.70  
  Purchase #3 $88.51   5.720%   $93.5728   $93.57   $93.55   $93.60  
  Purchase #4 $99.50   4.211%   $103.6899   $103.69   $103.70   $103.70  
  Purchase #5 $64.44   5.698%   $68.1118   $68.11   $68.10   $68.10  
  Purchase #6 $215.76   4.450%   $225.3613   $225.36   $225.35   $225.40  
  Purchase #7 $73.46   5.357%   $77.3953   $77.40   $77.40   $77.40  
  7 purchase totals = $827.29       $875.4806   $875.48   $875.45   $875.50