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 $92.45   4.472%   $96.5844   $96.58   $96.60   $96.60  
  Purchase #2 $102.94   10.191%   $113.4306   $113.43   $113.45   $113.40  
  Purchase #3 $58.97   11.472%   $65.735   $65.74   $65.75   $65.70  
  Purchase #4 $92.88   6.130%   $98.5735   $98.57   $98.55   $98.60  
  Purchase #5 $109.31   4.553%   $114.2869   $114.29   $114.30   $114.30  
  Purchase #6 $219.88   5.850%   $232.743   $232.74   $232.75   $232.70  
  Purchase #7 $65.78   10.452%   $72.6553   $72.66   $72.65   $72.70  
  7 purchase totals = $742.21       $794.0087   $794.01   $794.05   $794.00