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 $214.26   3.566%   $221.9005   $221.90   $221.90   $221.90  
  Purchase #2 $43.95   13.860%   $50.0415   $50.04   $50.05   $50.00  
  Purchase #3 $134.40   13.135%   $152.0534   $152.05   $152.05   $152.10  
  Purchase #4 $59.82   12.541%   $67.322   $67.32   $67.30   $67.30  
  Purchase #5 $239.37   10.722%   $265.0353   $265.04   $265.05   $265.00  
  Purchase #6 $65.62   9.142%   $71.619   $71.62   $71.60   $71.60  
  Purchase #7 $45.71   3.442%   $47.2833   $47.28   $47.30   $47.30  
  7 purchase totals = $803.13       $875.2550   $875.25   $875.25   $875.20