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 $162.90   8.259%   $176.3539   $176.35   $176.35   $176.40  
  Purchase #2 $114.94   9.663%   $126.0467   $126.05   $126.05   $126.00  
  Purchase #3 $241.45   6.676%   $257.5692   $257.57   $257.55   $257.60  
  Purchase #4 $126.30   12.453%   $142.0281   $142.03   $142.05   $142.00  
  Purchase #5 $60.51   11.751%   $67.6205   $67.62   $67.60   $67.60  
  Purchase #6 $223.73   6.402%   $238.0532   $238.05   $238.05   $238.10  
  Purchase #7 $201.32   8.284%   $217.9973   $218.00   $218.00   $218.00  
  7 purchase totals = $1,131.15       $1,225.6689   $1,225.67   $1,225.65   $1,225.70