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 $43.92   4.693%   $45.9812   $45.98   $46.00   $46.00  
  Purchase #2 $231.77   13.597%   $263.2838   $263.28   $263.30   $263.30  
  Purchase #3 $34.45   11.661%   $38.4672   $38.47   $38.45   $38.50  
  Purchase #4 $246.75   12.233%   $276.9349   $276.93   $276.95   $276.90  
  Purchase #5 $158.98   5.274%   $167.3646   $167.36   $167.35   $167.40  
  Purchase #6 $124.98   8.480%   $135.5783   $135.58   $135.60   $135.60  
  Purchase #7 $62.25   10.497%   $68.7844   $68.78   $68.80   $68.80  
  7 purchase totals = $903.10       $996.3944   $996.38   $996.45   $996.50