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 $43.41   7.252%   $46.5581   $46.56   $46.55   $46.60  
  Purchase #2 $113.46   10.268%   $125.1101   $125.11   $125.10   $125.10  
  Purchase #3 $119.58   11.250%   $133.0328   $133.03   $133.05   $133.00  
  Purchase #4 $231.97   9.583%   $254.1997   $254.20   $254.20   $254.20  
  Purchase #5 $221.86   10.289%   $244.6872   $244.69   $244.70   $244.70  
  Purchase #6 $169.62   3.144%   $174.9529   $174.95   $174.95   $175.00  
  Purchase #7 $66.53   12.684%   $74.9687   $74.97   $74.95   $75.00  
  7 purchase totals = $966.43       $1,053.5095   $1,053.51   $1,053.50   $1,053.60