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 $93.41   9.684%   $102.4558   $102.46   $102.45   $102.50  
  Purchase #2 $51.92   3.659%   $53.8198   $53.82   $53.80   $53.80  
  Purchase #3 $68.36   7.638%   $73.5813   $73.58   $73.60   $73.60  
  Purchase #4 $245.50   12.660%   $276.5803   $276.58   $276.60   $276.60  
  Purchase #5 $47.58   13.173%   $53.8477   $53.85   $53.85   $53.80  
  Purchase #6 $248.71   12.869%   $280.7165   $280.72   $280.70   $280.70  
  Purchase #7 $153.98   10.254%   $169.7691   $169.77   $169.75   $169.80  
  7 purchase totals = $909.46       $1,010.7705   $1,010.78   $1,010.75   $1,010.80