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 $55.46   9.292%   $60.6133   $60.61   $60.60   $60.60  
  Purchase #2 $206.28   4.663%   $215.8988   $215.90   $215.90   $215.90  
  Purchase #3 $84.86   3.805%   $88.0889   $88.09   $88.10   $88.10  
  Purchase #4 $159.56   12.636%   $179.722   $179.72   $179.70   $179.70  
  Purchase #5 $147.78   3.657%   $153.1843   $153.18   $153.20   $153.20  
  Purchase #6 $143.50   4.862%   $150.477   $150.48   $150.50   $150.50  
  Purchase #7 $86.41   7.826%   $93.1724   $93.17   $93.15   $93.20  
  7 purchase totals = $883.85       $941.1567   $941.15   $941.15   $941.20