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 $182.46   7.836%   $196.7576   $196.76   $196.75   $196.80  
  Purchase #2 $40.42   13.803%   $45.9992   $46.00   $46.00   $46.00  
  Purchase #3 $65.53   12.470%   $73.7016   $73.70   $73.70   $73.70  
  Purchase #4 $194.94   4.430%   $203.5758   $203.58   $203.60   $203.60  
  Purchase #5 $54.59   3.688%   $56.6033   $56.60   $56.60   $56.60  
  Purchase #6 $123.33   8.149%   $133.3802   $133.38   $133.40   $133.40  
  Purchase #7 $90.87   11.490%   $101.311   $101.31   $101.30   $101.30  
  7 purchase totals = $752.14       $811.3287   $811.33   $811.35   $811.40