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 $145.95   11.134%   $162.2001   $162.20   $162.20   $162.20  
  Purchase #2 $241.69   10.796%   $267.7829   $267.78   $267.80   $267.80  
  Purchase #3 $114.74   3.785%   $119.0829   $119.08   $119.10   $119.10  
  Purchase #4 $99.43   5.323%   $104.7227   $104.72   $104.70   $104.70  
  Purchase #5 $39.65   7.599%   $42.663   $42.66   $42.65   $42.70  
  Purchase #6 $230.86   7.157%   $247.3827   $247.38   $247.40   $247.40  
  Purchase #7 $163.60   4.387%   $170.7771   $170.78   $170.80   $170.80  
  7 purchase totals = $1,035.92       $1,114.6114   $1,114.60   $1,114.65   $1,114.70