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 $248.91   8.309%   $269.5919   $269.59   $269.60   $269.60  
  Purchase #2 $59.86   13.477%   $67.9273   $67.93   $67.95   $67.90  
  Purchase #3 $45.58   3.579%   $47.2113   $47.21   $47.20   $47.20  
  Purchase #4 $231.65   4.251%   $241.4974   $241.50   $241.50   $241.50  
  Purchase #5 $231.73   3.142%   $239.011   $239.01   $239.00   $239.00  
  Purchase #6 $130.92   5.166%   $137.6833   $137.68   $137.70   $137.70  
  Purchase #7 $96.79   5.816%   $102.4193   $102.42   $102.40   $102.40  
  7 purchase totals = $1,045.44       $1,105.3415   $1,105.34   $1,105.35   $1,105.30