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 $41.95   13.416%   $47.578   $47.58   $47.60   $47.60  
  Purchase #2 $86.36   6.448%   $91.9285   $91.93   $91.95   $91.90  
  Purchase #3 $31.75   10.173%   $34.9799   $34.98   $35.00   $35.00  
  Purchase #4 $43.88   7.363%   $47.1109   $47.11   $47.10   $47.10  
  Purchase #5 $106.59   7.285%   $114.3551   $114.36   $114.35   $114.40  
  Purchase #6 $204.47   9.869%   $224.6491   $224.65   $224.65   $224.60  
  Purchase #7 $195.26   13.190%   $221.0148   $221.01   $221.00   $221.00  
  7 purchase totals = $710.26       $781.6163   $781.62   $781.65   $781.60