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 $157.56   3.658%   $163.3235   $163.32   $163.30   $163.30  
  Purchase #2 $44.37   8.292%   $48.0492   $48.05   $48.05   $48.00  
  Purchase #3 $160.46   8.781%   $174.55   $174.55   $174.55   $174.60  
  Purchase #4 $91.78   10.333%   $101.2636   $101.26   $101.25   $101.30  
  Purchase #5 $147.73   3.358%   $152.6908   $152.69   $152.70   $152.70  
  Purchase #6 $197.54   13.643%   $224.4904   $224.49   $224.50   $224.50  
  Purchase #7 $154.25   4.521%   $161.2236   $161.22   $161.20   $161.20  
  7 purchase totals = $953.69       $1,025.5911   $1,025.58   $1,025.55   $1,025.60