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 $154.97   13.235%   $175.4803   $175.48   $175.50   $175.50  
  Purchase #2 $10.68   8.259%   $11.5621   $11.56   $11.55   $11.60  
  Purchase #3 $44.40   4.193%   $46.2617   $46.26   $46.25   $46.30  
  Purchase #4 $186.47   6.224%   $198.0759   $198.08   $198.10   $198.10  
  Purchase #5 $222.89   10.437%   $246.153   $246.15   $246.15   $246.20  
  Purchase #6 $115.86   3.485%   $119.8977   $119.90   $119.90   $119.90  
  Purchase #7 $195.53   9.790%   $214.6724   $214.67   $214.65   $214.70  
  7 purchase totals = $930.80       $1,012.1031   $1,012.10   $1,012.10   $1,012.30