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 $194.37   3.641%   $201.447   $201.45   $201.45   $201.40  
  Purchase #2 $32.75   13.348%   $37.1215   $37.12   $37.10   $37.10  
  Purchase #3 $73.55   11.159%   $81.7574   $81.76   $81.75   $81.80  
  Purchase #4 $60.70   10.342%   $66.9776   $66.98   $67.00   $67.00  
  Purchase #5 $230.49   7.655%   $248.134   $248.13   $248.15   $248.10  
  Purchase #6 $23.72   3.121%   $24.4603   $24.46   $24.45   $24.50  
  Purchase #7 $40.60   7.339%   $43.5796   $43.58   $43.60   $43.60  
  7 purchase totals = $656.18       $703.4774   $703.48   $703.50   $703.50