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 $45.31   5.173%   $47.6539   $47.65   $47.65   $47.70  
  Purchase #2 $42.61   11.840%   $47.655   $47.66   $47.65   $47.70  
  Purchase #3 $109.78   7.581%   $118.1024   $118.10   $118.10   $118.10  
  Purchase #4 $100.26   12.189%   $112.4807   $112.48   $112.50   $112.50  
  Purchase #5 $186.51   13.493%   $211.6758   $211.68   $211.70   $211.70  
  Purchase #6 $226.26   10.872%   $250.859   $250.86   $250.85   $250.90  
  Purchase #7 $160.60   7.784%   $173.1011   $173.10   $173.10   $173.10  
  7 purchase totals = $871.33       $961.5279   $961.53   $961.55   $961.70