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 $93.94   3.309%   $97.0485   $97.05   $97.05   $97.00  
  Purchase #2 $182.30   10.112%   $200.7342   $200.73   $200.75   $200.70  
  Purchase #3 $207.25   10.215%   $228.4206   $228.42   $228.40   $228.40  
  Purchase #4 $145.68   9.499%   $159.5181   $159.52   $159.50   $159.50  
  Purchase #5 $44.45   6.127%   $47.1735   $47.17   $47.15   $47.20  
  Purchase #6 $138.43   12.624%   $155.9054   $155.91   $155.90   $155.90  
  Purchase #7 $71.70   9.265%   $78.343   $78.34   $78.35   $78.30  
  7 purchase totals = $883.75       $967.1433   $967.14   $967.10   $967.00