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 $58.45   7.127%   $62.6157   $62.62   $62.60   $62.60  
  Purchase #2 $95.73   13.292%   $108.4544   $108.45   $108.45   $108.50  
  Purchase #3 $171.68   12.813%   $193.6774   $193.68   $193.70   $193.70  
  Purchase #4 $233.86   13.534%   $265.5106   $265.51   $265.50   $265.50  
  Purchase #5 $131.98   6.395%   $140.4201   $140.42   $140.40   $140.40  
  Purchase #6 $221.65   11.188%   $246.4482   $246.45   $246.45   $246.40  
  Purchase #7 $108.30   11.133%   $120.357   $120.36   $120.35   $120.40  
  7 purchase totals = $1,021.65       $1,137.4834   $1,137.49   $1,137.45   $1,137.50