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 $84.79   13.353%   $96.112   $96.11   $96.10   $96.10  
  Purchase #2 $244.51   8.774%   $265.9633   $265.96   $265.95   $266.00  
  Purchase #3 $161.26   12.826%   $181.9432   $181.94   $181.95   $181.90  
  Purchase #4 $229.52   9.211%   $250.6611   $250.66   $250.65   $250.70  
  Purchase #5 $123.45   3.187%   $127.3844   $127.38   $127.40   $127.40  
  Purchase #6 $103.95   9.588%   $113.9167   $113.92   $113.90   $113.90  
  Purchase #7 $62.78   12.622%   $70.7041   $70.70   $70.70   $70.70  
  7 purchase totals = $1,010.26       $1,106.6848   $1,106.67   $1,106.65   $1,106.70