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 $204.48   3.564%   $211.7677   $211.77   $211.75   $211.80  
  Purchase #2 $68.87   6.499%   $73.3459   $73.35   $73.35   $73.30  
  Purchase #3 $50.81   3.459%   $52.5675   $52.57   $52.55   $52.60  
  Purchase #4 $34.99   7.431%   $37.5901   $37.59   $37.60   $37.60  
  Purchase #5 $201.90   7.232%   $216.5014   $216.50   $216.50   $216.50  
  Purchase #6 $200.36   12.796%   $225.9981   $226.00   $226.00   $226.00  
  Purchase #7 $101.63   6.342%   $108.0754   $108.08   $108.10   $108.10  
  7 purchase totals = $863.04       $925.8461   $925.86   $925.85   $925.90