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 $187.53   4.361%   $195.7082   $195.71   $195.70   $195.70  
  Purchase #2 $149.97   11.156%   $166.7007   $166.70   $166.70   $166.70  
  Purchase #3 $132.38   5.572%   $139.7562   $139.76   $139.75   $139.80  
  Purchase #4 $164.93   10.791%   $182.7276   $182.73   $182.75   $182.70  
  Purchase #5 $175.96   5.514%   $185.6624   $185.66   $185.65   $185.70  
  Purchase #6 $168.40   6.716%   $179.7097   $179.71   $179.70   $179.70  
  Purchase #7 $145.71   5.362%   $153.523   $153.52   $153.50   $153.50  
  7 purchase totals = $1,124.88       $1,203.7878   $1,203.79   $1,203.75   $1,203.80