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 $174.86   13.146%   $197.8471   $197.85   $197.85   $197.80  
  Purchase #2 $147.44   11.705%   $164.6979   $164.70   $164.70   $164.70  
  Purchase #3 $73.77   4.341%   $76.9724   $76.97   $76.95   $77.00  
  Purchase #4 $37.80   11.241%   $42.0491   $42.05   $42.05   $42.00  
  Purchase #5 $195.67   3.445%   $202.4108   $202.41   $202.40   $202.40  
  Purchase #6 $112.74   6.326%   $119.8719   $119.87   $119.85   $119.90  
  Purchase #7 $220.42   12.239%   $247.3972   $247.40   $247.40   $247.40  
  7 purchase totals = $962.70       $1,051.2464   $1,051.25   $1,051.20   $1,051.20