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 $41.35   7.595%   $44.4905   $44.49   $44.50   $44.50  
  Purchase #2 $169.36   3.626%   $175.501   $175.50   $175.50   $175.50  
  Purchase #3 $171.47   13.243%   $194.1778   $194.18   $194.20   $194.20  
  Purchase #4 $238.58   13.459%   $270.6905   $270.69   $270.70   $270.70  
  Purchase #5 $166.37   13.317%   $188.5255   $188.53   $188.55   $188.50  
  Purchase #6 $15.95   5.782%   $16.8722   $16.87   $16.85   $16.90  
  Purchase #7 $222.44   9.692%   $243.9989   $244.00   $244.00   $244.00  
  7 purchase totals = $1,025.52       $1,134.2564   $1,134.26   $1,134.30   $1,134.30