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 $65.67   10.111%   $72.3099   $72.31   $72.30   $72.30  
  Purchase #2 $171.78   11.653%   $191.7975   $191.80   $191.80   $191.80  
  Purchase #3 $12.51   11.604%   $13.9617   $13.96   $13.95   $14.00  
  Purchase #4 $57.25   9.417%   $62.6412   $62.64   $62.65   $62.60  
  Purchase #5 $91.81   11.802%   $102.6454   $102.65   $102.65   $102.60  
  Purchase #6 $250.38   4.640%   $261.9976   $262.00   $262.00   $262.00  
  Purchase #7 $25.28   5.327%   $26.6267   $26.63   $26.65   $26.60  
  7 purchase totals = $674.68       $731.9800   $731.99   $732.00   $731.90