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 $59.26   7.368%   $63.6263   $63.63   $63.65   $63.60  
  Purchase #2 $159.35   5.601%   $168.2752   $168.28   $168.30   $168.30  
  Purchase #3 $51.62   5.356%   $54.3848   $54.38   $54.40   $54.40  
  Purchase #4 $169.52   10.440%   $187.2179   $187.22   $187.20   $187.20  
  Purchase #5 $95.44   7.691%   $102.7803   $102.78   $102.80   $102.80  
  Purchase #6 $144.72   12.220%   $162.4048   $162.40   $162.40   $162.40  
  Purchase #7 $51.93   10.150%   $57.2009   $57.20   $57.20   $57.20  
  7 purchase totals = $731.84       $795.8902   $795.89   $795.95   $795.90