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 $41.96   5.842%   $44.4113   $44.41   $44.40   $44.40  
  Purchase #2 $127.49   10.225%   $140.5259   $140.53   $140.55   $140.50  
  Purchase #3 $133.28   12.563%   $150.024   $150.02   $150.00   $150.00  
  Purchase #4 $162.91   8.329%   $176.4788   $176.48   $176.50   $176.50  
  Purchase #5 $193.80   10.260%   $213.6839   $213.68   $213.70   $213.70  
  Purchase #6 $111.41   11.230%   $123.9213   $123.92   $123.90   $123.90  
  Purchase #7 $190.64   10.671%   $210.9832   $210.98   $211.00   $211.00  
  7 purchase totals = $961.49       $1,060.0284   $1,060.02   $1,060.05   $1,060.00