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 $85.25   12.301%   $95.7366   $95.74   $95.75   $95.70  
  Purchase #2 $191.48   9.278%   $209.2455   $209.25   $209.25   $209.20  
  Purchase #3 $181.49   12.164%   $203.5664   $203.57   $203.55   $203.60  
  Purchase #4 $63.26   4.643%   $66.1972   $66.20   $66.20   $66.20  
  Purchase #5 $123.44   10.826%   $136.8036   $136.80   $136.80   $136.80  
  Purchase #6 $225.31   7.745%   $242.7603   $242.76   $242.75   $242.80  
  Purchase #7 $233.30   8.620%   $253.4105   $253.41   $253.40   $253.40  
  7 purchase totals = $1,103.53       $1,207.7201   $1,207.73   $1,207.70   $1,207.70