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 $43.84   6.346%   $46.6221   $46.62   $46.60   $46.60  
  Purchase #2 $193.91   13.270%   $219.6419   $219.64   $219.65   $219.60  
  Purchase #3 $93.91   9.389%   $102.7272   $102.73   $102.75   $102.70  
  Purchase #4 $222.25   5.647%   $234.8005   $234.80   $234.80   $234.80  
  Purchase #5 $119.93   11.745%   $134.0158   $134.02   $134.00   $134.00  
  Purchase #6 $215.27   13.235%   $243.761   $243.76   $243.75   $243.80  
  Purchase #7 $176.55   7.477%   $189.7506   $189.75   $189.75   $189.80  
  7 purchase totals = $1,065.66       $1,171.3191   $1,171.32   $1,171.30   $1,171.30