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 $61.97   11.372%   $69.0172   $69.02   $69.00   $69.00  
  Purchase #2 $104.26   13.457%   $118.2903   $118.29   $118.30   $118.30  
  Purchase #3 $199.56   12.354%   $224.2136   $224.21   $224.20   $224.20  
  Purchase #4 $179.42   3.849%   $186.3259   $186.33   $186.35   $186.30  
  Purchase #5 $5.95   12.566%   $6.6977   $6.70   $6.70   $6.70  
  Purchase #6 $39.65   7.310%   $42.5484   $42.55   $42.55   $42.50  
  Purchase #7 $97.79   7.863%   $105.4792   $105.48   $105.50   $105.50  
  7 purchase totals = $688.60       $752.5723   $752.58   $752.60   $752.50