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 $65.87   4.795%   $69.0285   $69.03   $69.05   $69.00  
  Purchase #2 $213.96   10.502%   $236.4301   $236.43   $236.45   $236.40  
  Purchase #3 $68.96   3.637%   $71.4681   $71.47   $71.45   $71.50  
  Purchase #4 $206.85   13.637%   $235.0581   $235.06   $235.05   $235.10  
  Purchase #5 $54.50   6.397%   $57.9864   $57.99   $58.00   $58.00  
  Purchase #6 $241.49   12.282%   $271.1498   $271.15   $271.15   $271.10  
  Purchase #7 $151.84   10.765%   $168.1856   $168.19   $168.20   $168.20  
  7 purchase totals = $1,003.47       $1,109.3066   $1,109.32   $1,109.35   $1,109.30