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 $196.81   10.177%   $216.8394   $216.84   $216.85   $216.80  
  Purchase #2 $57.42   8.347%   $62.2128   $62.21   $62.20   $62.20  
  Purchase #3 $225.83   11.400%   $251.5746   $251.57   $251.55   $251.60  
  Purchase #4 $87.34   13.797%   $99.3903   $99.39   $99.40   $99.40  
  Purchase #5 $190.30   11.247%   $211.703   $211.70   $211.70   $211.70  
  Purchase #6 $228.81   5.571%   $241.557   $241.56   $241.55   $241.60  
  Purchase #7 $180.47   3.124%   $186.1079   $186.11   $186.10   $186.10  
  7 purchase totals = $1,166.98       $1,269.3850   $1,269.38   $1,269.35   $1,269.40