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 $203.29   9.584%   $222.7733   $222.77   $222.75   $222.80  
  Purchase #2 $209.48   4.416%   $218.7306   $218.73   $218.75   $218.70  
  Purchase #3 $56.78   5.752%   $60.046   $60.05   $60.05   $60.00  
  Purchase #4 $77.73   9.419%   $85.0514   $85.05   $85.05   $85.10  
  Purchase #5 $158.89   9.574%   $174.1021   $174.10   $174.10   $174.10  
  Purchase #6 $183.89   7.360%   $197.4243   $197.42   $197.40   $197.40  
  Purchase #7 $191.28   10.499%   $211.3625   $211.36   $211.35   $211.40  
  7 purchase totals = $1,081.34       $1,169.4902   $1,169.48   $1,169.45   $1,169.50