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 $44.61   6.565%   $47.5386   $47.54   $47.55   $47.50  
  Purchase #2 $145.32   6.187%   $154.3109   $154.31   $154.30   $154.30  
  Purchase #3 $212.43   6.711%   $226.6862   $226.69   $226.70   $226.70  
  Purchase #4 $10.93   7.672%   $11.7685   $11.77   $11.75   $11.80  
  Purchase #5 $101.30   6.731%   $108.1185   $108.12   $108.10   $108.10  
  Purchase #6 $112.97   6.609%   $120.4362   $120.44   $120.45   $120.40  
  Purchase #7 $105.34   12.116%   $118.103   $118.10   $118.10   $118.10  
  7 purchase totals = $732.90       $786.9619   $786.97   $786.95   $786.90