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 $59.92   4.155%   $62.4097   $62.41   $62.40   $62.40  
  Purchase #2 $219.56   6.128%   $233.0146   $233.01   $233.00   $233.00  
  Purchase #3 $113.53   11.802%   $126.9288   $126.93   $126.95   $126.90  
  Purchase #4 $178.74   11.393%   $199.1038   $199.10   $199.10   $199.10  
  Purchase #5 $166.76   11.455%   $185.8624   $185.86   $185.85   $185.90  
  Purchase #6 $222.67   11.245%   $247.7092   $247.71   $247.70   $247.70  
  Purchase #7 $24.99   4.719%   $26.1693   $26.17   $26.15   $26.20  
  7 purchase totals = $986.17       $1,081.1978   $1,081.19   $1,081.15   $1,081.20