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 $57.53   8.229%   $62.2641   $62.26   $62.25   $62.30  
  Purchase #2 $185.79   5.862%   $196.681   $196.68   $196.70   $196.70  
  Purchase #3 $83.84   4.749%   $87.8216   $87.82   $87.80   $87.80  
  Purchase #4 $162.72   11.311%   $181.1253   $181.13   $181.15   $181.10  
  Purchase #5 $245.52   10.738%   $271.8839   $271.88   $271.90   $271.90  
  Purchase #6 $239.74   8.711%   $260.6238   $260.62   $260.60   $260.60  
  Purchase #7 $10.61   13.533%   $12.0459   $12.05   $12.05   $12.00  
  7 purchase totals = $985.75       $1,072.4456   $1,072.44   $1,072.45   $1,072.40