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 $69.86   8.240%   $75.6165   $75.62   $75.60   $75.60  
  Purchase #2 $167.89   12.742%   $189.2825   $189.28   $189.30   $189.30  
  Purchase #3 $207.27   4.262%   $216.1038   $216.10   $216.10   $216.10  
  Purchase #4 $59.61   12.498%   $67.0601   $67.06   $67.05   $67.10  
  Purchase #5 $91.82   3.848%   $95.3532   $95.35   $95.35   $95.40  
  Purchase #6 $67.35   10.724%   $74.5726   $74.57   $74.55   $74.60  
  Purchase #7 $220.77   5.438%   $232.7755   $232.78   $232.80   $232.80  
  7 purchase totals = $884.57       $950.7642   $950.76   $950.75   $950.90