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 $64.93   7.133%   $69.5615   $69.56   $69.55   $69.60  
  Purchase #2 $35.41   5.269%   $37.2758   $37.28   $37.30   $37.30  
  Purchase #3 $206.81   4.515%   $216.1475   $216.15   $216.15   $216.10  
  Purchase #4 $248.33   6.798%   $265.2115   $265.21   $265.20   $265.20  
  Purchase #5 $24.46   11.167%   $27.1914   $27.19   $27.20   $27.20  
  Purchase #6 $241.43   6.664%   $257.5189   $257.52   $257.50   $257.50  
  Purchase #7 $154.46   5.621%   $163.1422   $163.14   $163.15   $163.10  
  7 purchase totals = $975.83       $1,036.0488   $1,036.05   $1,036.05   $1,036.00