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 $61.78   10.447%   $68.2342   $68.23   $68.25   $68.20  
  Purchase #2 $205.47   4.140%   $213.9765   $213.98   $214.00   $214.00  
  Purchase #3 $34.64   12.649%   $39.0216   $39.02   $39.00   $39.00  
  Purchase #4 $216.57   7.351%   $232.4901   $232.49   $232.50   $232.50  
  Purchase #5 $182.48   10.867%   $202.3101   $202.31   $202.30   $202.30  
  Purchase #6 $139.75   12.817%   $157.6618   $157.66   $157.65   $157.70  
  Purchase #7 $197.28   13.253%   $223.4255   $223.43   $223.45   $223.40  
  7 purchase totals = $1,037.97       $1,137.1198   $1,137.12   $1,137.15   $1,137.10