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 $82.54   13.521%   $93.7002   $93.70   $93.70   $93.70  
  Purchase #2 $113.77   13.662%   $129.3133   $129.31   $129.30   $129.30  
  Purchase #3 $9.96   4.541%   $10.4123   $10.41   $10.40   $10.40  
  Purchase #4 $193.88   9.172%   $211.6627   $211.66   $211.65   $211.70  
  Purchase #5 $189.67   12.551%   $213.4755   $213.48   $213.50   $213.50  
  Purchase #6 $19.25   7.471%   $20.6882   $20.69   $20.70   $20.70  
  Purchase #7 $112.97   7.790%   $121.7704   $121.77   $121.75   $121.80  
  7 purchase totals = $722.04       $801.0226   $801.02   $801.00   $801.10