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 $72.91   4.196%   $75.9693   $75.97   $75.95   $76.00  
  Purchase #2 $235.97   13.157%   $267.0166   $267.02   $267.00   $267.00  
  Purchase #3 $67.86   6.349%   $72.1684   $72.17   $72.15   $72.20  
  Purchase #4 $240.42   9.575%   $263.4402   $263.44   $263.45   $263.40  
  Purchase #5 $233.69   7.224%   $250.5718   $250.57   $250.55   $250.60  
  Purchase #6 $98.44   5.267%   $103.6248   $103.62   $103.60   $103.60  
  Purchase #7 $140.73   7.599%   $151.4241   $151.42   $151.40   $151.40  
  7 purchase totals = $1,090.02       $1,184.2152   $1,184.21   $1,184.10   $1,184.20