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 $24.93   4.293%   $26.0002   $26.00   $26.00   $26.00  
  Purchase #2 $64.35   3.580%   $66.6537   $66.65   $66.65   $66.70  
  Purchase #3 $39.29   12.300%   $44.1227   $44.12   $44.10   $44.10  
  Purchase #4 $156.93   11.735%   $175.3457   $175.35   $175.35   $175.30  
  Purchase #5 $59.48   10.368%   $65.6469   $65.65   $65.65   $65.60  
  Purchase #6 $247.51   6.708%   $264.113   $264.11   $264.10   $264.10  
  Purchase #7 $101.78   10.372%   $112.3366   $112.34   $112.35   $112.30  
  7 purchase totals = $694.27       $754.2188   $754.22   $754.20   $754.10