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 $113.88   9.798%   $125.038   $125.04   $125.05   $125.00  
  Purchase #2 $22.72   11.294%   $25.286   $25.29   $25.30   $25.30  
  Purchase #3 $42.74   9.480%   $46.7918   $46.79   $46.80   $46.80  
  Purchase #4 $65.31   11.729%   $72.9702   $72.97   $72.95   $73.00  
  Purchase #5 $88.69   10.553%   $98.0495   $98.05   $98.05   $98.00  
  Purchase #6 $243.35   13.414%   $275.993   $275.99   $276.00   $276.00  
  Purchase #7 $231.31   3.287%   $238.9132   $238.91   $238.90   $238.90  
  7 purchase totals = $808.00       $883.0417   $883.04   $883.05   $883.00