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 $194.61   3.771%   $201.9487   $201.95   $201.95   $201.90  
  Purchase #2 $238.74   7.516%   $256.6837   $256.68   $256.70   $256.70  
  Purchase #3 $157.49   4.458%   $164.5109   $164.51   $164.50   $164.50  
  Purchase #4 $46.92   3.360%   $48.4965   $48.50   $48.50   $48.50  
  Purchase #5 $175.71   4.586%   $183.7681   $183.77   $183.75   $183.80  
  Purchase #6 $231.78   8.339%   $251.1081   $251.11   $251.10   $251.10  
  Purchase #7 $120.41   4.641%   $125.9982   $126.00   $126.00   $126.00  
  7 purchase totals = $1,165.66       $1,232.5142   $1,232.52   $1,232.50   $1,232.50