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 $58.59   4.425%   $61.1826   $61.18   $61.20   $61.20  
  Purchase #2 $201.97   10.550%   $223.2778   $223.28   $223.30   $223.30  
  Purchase #3 $132.38   11.601%   $147.7374   $147.74   $147.75   $147.70  
  Purchase #4 $246.74   10.194%   $271.8927   $271.89   $271.90   $271.90  
  Purchase #5 $124.50   12.519%   $140.0862   $140.09   $140.10   $140.10  
  Purchase #6 $166.50   5.439%   $175.5559   $175.56   $175.55   $175.60  
  Purchase #7 $237.71   4.221%   $247.7437   $247.74   $247.75   $247.70  
  7 purchase totals = $1,168.39       $1,267.4763   $1,267.48   $1,267.55   $1,267.50