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 $92.30   13.722%   $104.9654   $104.97   $104.95   $105.00  
  Purchase #2 $88.31   7.386%   $94.8326   $94.83   $94.85   $94.80  
  Purchase #3 $193.31   12.722%   $217.9029   $217.90   $217.90   $217.90  
  Purchase #4 $174.64   8.572%   $189.6101   $189.61   $189.60   $189.60  
  Purchase #5 $31.66   6.559%   $33.7366   $33.74   $33.75   $33.70  
  Purchase #6 $191.40   8.281%   $207.2498   $207.25   $207.25   $207.20  
  Purchase #7 $246.54   5.223%   $259.4168   $259.42   $259.40   $259.40  
  7 purchase totals = $1,018.16       $1,107.7142   $1,107.72   $1,107.70   $1,107.60