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 $58.91   3.508%   $60.9766   $60.98   $61.00   $61.00  
  Purchase #2 $110.71   8.139%   $119.7207   $119.72   $119.70   $119.70  
  Purchase #3 $179.61   8.568%   $194.999   $195.00   $195.00   $195.00  
  Purchase #4 $158.67   12.819%   $179.0099   $179.01   $179.00   $179.00  
  Purchase #5 $80.97   8.272%   $87.6678   $87.67   $87.65   $87.70  
  Purchase #6 $90.97   8.562%   $98.7589   $98.76   $98.75   $98.80  
  Purchase #7 $194.70   7.239%   $208.7943   $208.79   $208.80   $208.80  
  7 purchase totals = $874.54       $949.9272   $949.93   $949.90   $950.00