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 $195.68   10.691%   $216.6001   $216.60   $216.60   $216.60  
  Purchase #2 $152.72   8.207%   $165.2537   $165.25   $165.25   $165.30  
  Purchase #3 $114.47   10.290%   $126.249   $126.25   $126.25   $126.20  
  Purchase #4 $33.52   9.239%   $36.6169   $36.62   $36.60   $36.60  
  Purchase #5 $127.96   4.373%   $133.5557   $133.56   $133.55   $133.60  
  Purchase #6 $22.71   13.874%   $25.8608   $25.86   $25.85   $25.90  
  Purchase #7 $152.38   3.581%   $157.8367   $157.84   $157.85   $157.80  
  7 purchase totals = $799.44       $861.9729   $861.98   $861.95   $862.00