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 $209.66   7.308%   $224.982   $224.98   $225.00   $225.00  
  Purchase #2 $5.64   12.394%   $6.339   $6.34   $6.35   $6.30  
  Purchase #3 $234.63   6.351%   $249.5314   $249.53   $249.55   $249.50  
  Purchase #4 $15.86   13.624%   $18.0208   $18.02   $18.00   $18.00  
  Purchase #5 $61.35   6.854%   $65.5549   $65.55   $65.55   $65.60  
  Purchase #6 $204.84   3.279%   $211.5567   $211.56   $211.55   $211.60  
  Purchase #7 $216.68   8.294%   $234.6514   $234.65   $234.65   $234.70  
  7 purchase totals = $948.66       $1,010.6362   $1,010.63   $1,010.65   $1,010.70