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 $13.94   5.387%   $14.6909   $14.69   $14.70   $14.70  
  Purchase #2 $225.51   8.118%   $243.8169   $243.82   $243.80   $243.80  
  Purchase #3 $194.94   4.782%   $204.262   $204.26   $204.25   $204.30  
  Purchase #4 $42.77   9.390%   $46.7861   $46.79   $46.80   $46.80  
  Purchase #5 $97.36   8.276%   $105.4175   $105.42   $105.40   $105.40  
  Purchase #6 $91.38   13.164%   $103.4093   $103.41   $103.40   $103.40  
  Purchase #7 $201.28   8.737%   $218.8658   $218.87   $218.85   $218.90  
  7 purchase totals = $867.18       $937.2485   $937.26   $937.20   $937.30