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 $88.59   7.488%   $95.2236   $95.22   $95.20   $95.20  
  Purchase #2 $5.46   9.549%   $5.9814   $5.98   $6.00   $6.00  
  Purchase #3 $113.83   8.354%   $123.3394   $123.34   $123.35   $123.30  
  Purchase #4 $67.80   6.109%   $71.9419   $71.94   $71.95   $71.90  
  Purchase #5 $13.35   7.408%   $14.339   $14.34   $14.35   $14.30  
  Purchase #6 $33.72   5.257%   $35.4927   $35.49   $35.50   $35.50  
  Purchase #7 $207.96   5.284%   $218.9486   $218.95   $218.95   $218.90  
  7 purchase totals = $530.71       $565.2666   $565.26   $565.30   $565.10