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 $196.38   3.236%   $202.7349   $202.73   $202.75   $202.70  
  Purchase #2 $175.36   10.232%   $193.3028   $193.30   $193.30   $193.30  
  Purchase #3 $246.30   6.650%   $262.679   $262.68   $262.70   $262.70  
  Purchase #4 $113.29   6.700%   $120.8804   $120.88   $120.90   $120.90  
  Purchase #5 $140.55   8.670%   $152.7357   $152.74   $152.75   $152.70  
  Purchase #6 $93.50   3.161%   $96.4555   $96.46   $96.45   $96.50  
  Purchase #7 $149.54   12.812%   $168.6991   $168.70   $168.70   $168.70  
  7 purchase totals = $1,114.92       $1,197.4874   $1,197.49   $1,197.55   $1,197.50