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 $65.89   3.139%   $67.9583   $67.96   $67.95   $68.00  
  Purchase #2 $220.42   5.267%   $232.0295   $232.03   $232.05   $232.00  
  Purchase #3 $41.80   10.369%   $46.1342   $46.13   $46.15   $46.10  
  Purchase #4 $181.89   13.733%   $206.869   $206.87   $206.85   $206.90  
  Purchase #5 $123.58   5.439%   $130.3015   $130.30   $130.30   $130.30  
  Purchase #6 $250.61   6.733%   $267.4836   $267.48   $267.50   $267.50  
  Purchase #7 $198.94   11.303%   $221.4262   $221.43   $221.45   $221.40  
  7 purchase totals = $1,083.13       $1,172.2023   $1,172.20   $1,172.25   $1,172.20