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 $107.64   6.611%   $114.7561   $114.76   $114.75   $114.80  
  Purchase #2 $109.39   6.718%   $116.7388   $116.74   $116.75   $116.70  
  Purchase #3 $228.52   5.634%   $241.3948   $241.39   $241.40   $241.40  
  Purchase #4 $14.70   13.254%   $16.6483   $16.65   $16.65   $16.60  
  Purchase #5 $102.90   12.722%   $115.9909   $115.99   $116.00   $116.00  
  Purchase #6 $237.71   9.557%   $260.4279   $260.43   $260.45   $260.40  
  Purchase #7 $27.27   6.816%   $29.1287   $29.13   $29.15   $29.10  
  7 purchase totals = $828.13       $895.0855   $895.09   $895.15   $895.00