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 $42.95   7.150%   $46.0209   $46.02   $46.00   $46.00  
  Purchase #2 $117.75   6.454%   $125.3496   $125.35   $125.35   $125.30  
  Purchase #3 $94.82   6.225%   $100.7225   $100.72   $100.70   $100.70  
  Purchase #4 $249.57   10.743%   $276.3813   $276.38   $276.40   $276.40  
  Purchase #5 $103.59   6.353%   $110.1711   $110.17   $110.15   $110.20  
  Purchase #6 $185.69   9.652%   $203.6128   $203.61   $203.60   $203.60  
  Purchase #7 $121.41   13.655%   $137.9885   $137.99   $138.00   $138.00  
  7 purchase totals = $915.78       $1,000.2467   $1,000.24   $1,000.20   $1,000.20