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 $166.74   4.365%   $174.0182   $174.02   $174.00   $174.00  
  Purchase #2 $60.33   5.520%   $63.6602   $63.66   $63.65   $63.70  
  Purchase #3 $207.99   5.602%   $219.6416   $219.64   $219.65   $219.60  
  Purchase #4 $118.57   3.408%   $122.6109   $122.61   $122.60   $122.60  
  Purchase #5 $210.51   10.335%   $232.2662   $232.27   $232.25   $232.30  
  Purchase #6 $191.71   12.690%   $216.038   $216.04   $216.05   $216.00  
  Purchase #7 $5.69   11.616%   $6.351   $6.35   $6.35   $6.40  
  7 purchase totals = $961.54       $1,034.5861   $1,034.59   $1,034.55   $1,034.60