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 $67.37   9.515%   $73.7803   $73.78   $73.80   $73.80  
  Purchase #2 $216.76   8.405%   $234.9787   $234.98   $235.00   $235.00  
  Purchase #3 $19.85   12.144%   $22.2606   $22.26   $22.25   $22.30  
  Purchase #4 $216.94   11.536%   $241.9662   $241.97   $241.95   $242.00  
  Purchase #5 $238.29   6.831%   $254.5676   $254.57   $254.55   $254.60  
  Purchase #6 $38.61   11.361%   $42.9965   $43.00   $43.00   $43.00  
  Purchase #7 $111.40   3.605%   $115.416   $115.42   $115.40   $115.40  
  7 purchase totals = $909.22       $985.9659   $985.98   $985.95   $986.10