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 $46.38   3.602%   $48.0506   $48.05   $48.05   $48.10  
  Purchase #2 $195.32   13.756%   $222.1882   $222.19   $222.20   $222.20  
  Purchase #3 $88.31   5.760%   $93.3967   $93.40   $93.40   $93.40  
  Purchase #4 $110.44   10.287%   $121.801   $121.80   $121.80   $121.80  
  Purchase #5 $212.32   13.220%   $240.3887   $240.39   $240.40   $240.40  
  Purchase #6 $96.50   13.316%   $109.3499   $109.35   $109.35   $109.30  
  Purchase #7 $239.35   12.455%   $269.161   $269.16   $269.15   $269.20  
  7 purchase totals = $988.62       $1,104.3361   $1,104.34   $1,104.35   $1,104.40