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 $174.32   13.127%   $197.203   $197.20   $197.20   $197.20  
  Purchase #2 $44.76   9.131%   $48.847   $48.85   $48.85   $48.80  
  Purchase #3 $147.49   7.407%   $158.4146   $158.41   $158.40   $158.40  
  Purchase #4 $68.69   3.475%   $71.077   $71.08   $71.10   $71.10  
  Purchase #5 $138.54   11.833%   $154.9334   $154.93   $154.95   $154.90  
  Purchase #6 $216.56   6.140%   $229.8568   $229.86   $229.85   $229.90  
  Purchase #7 $194.83   8.577%   $211.5406   $211.54   $211.55   $211.50  
  7 purchase totals = $985.19       $1,071.8724   $1,071.87   $1,071.90   $1,071.80