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 $96.75   5.309%   $101.8865   $101.89   $101.90   $101.90  
  Purchase #2 $215.39   11.309%   $239.7485   $239.75   $239.75   $239.70  
  Purchase #3 $165.34   5.441%   $174.3361   $174.34   $174.35   $174.30  
  Purchase #4 $158.71   3.516%   $164.2902   $164.29   $164.30   $164.30  
  Purchase #5 $32.57   11.141%   $36.1986   $36.20   $36.20   $36.20  
  Purchase #6 $234.93   9.121%   $256.358   $256.36   $256.35   $256.40  
  Purchase #7 $160.92   11.648%   $179.664   $179.66   $179.65   $179.70  
  7 purchase totals = $1,064.61       $1,152.4819   $1,152.49   $1,152.50   $1,152.50