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 $210.85   9.408%   $230.6868   $230.69   $230.70   $230.70  
  Purchase #2 $164.93   11.239%   $183.4665   $183.47   $183.45   $183.50  
  Purchase #3 $41.38   12.132%   $46.4002   $46.40   $46.40   $46.40  
  Purchase #4 $210.32   8.557%   $228.3171   $228.32   $228.30   $228.30  
  Purchase #5 $161.31   8.297%   $174.6939   $174.69   $174.70   $174.70  
  Purchase #6 $203.94   8.556%   $221.3891   $221.39   $221.40   $221.40  
  Purchase #7 $198.89   9.457%   $217.699   $217.70   $217.70   $217.70  
  7 purchase totals = $1,191.62       $1,302.6526   $1,302.66   $1,302.65   $1,302.70