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 $211.90   11.216%   $235.6667   $235.67   $235.65   $235.70  
  Purchase #2 $141.76   10.343%   $156.4222   $156.42   $156.40   $156.40  
  Purchase #3 $58.33   3.816%   $60.5559   $60.56   $60.55   $60.60  
  Purchase #4 $51.92   12.326%   $58.3197   $58.32   $58.30   $58.30  
  Purchase #5 $186.77   3.769%   $193.8094   $193.81   $193.80   $193.80  
  Purchase #6 $210.93   9.181%   $230.2955   $230.30   $230.30   $230.30  
  Purchase #7 $205.29   12.726%   $231.4152   $231.42   $231.40   $231.40  
  7 purchase totals = $1,066.90       $1,166.4846   $1,166.50   $1,166.40   $1,166.50