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 $168.72   5.725%   $178.3792   $178.38   $178.40   $178.40  
  Purchase #2 $67.82   10.411%   $74.8807   $74.88   $74.90   $74.90  
  Purchase #3 $73.90   11.862%   $82.666   $82.67   $82.65   $82.70  
  Purchase #4 $98.66   7.230%   $105.7931   $105.79   $105.80   $105.80  
  Purchase #5 $238.59   11.620%   $266.3142   $266.31   $266.30   $266.30  
  Purchase #6 $145.99   9.549%   $159.9306   $159.93   $159.95   $159.90  
  Purchase #7 $135.43   7.832%   $146.0369   $146.04   $146.05   $146.00  
  7 purchase totals = $929.11       $1,014.0007   $1,014.00   $1,014.05   $1,014.00