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 $92.54   3.797%   $96.0537   $96.05   $96.05   $96.10  
  Purchase #2 $11.42   6.853%   $12.2026   $12.20   $12.20   $12.20  
  Purchase #3 $145.54   7.849%   $156.9634   $156.96   $156.95   $157.00  
  Purchase #4 $93.59   11.525%   $104.3762   $104.38   $104.40   $104.40  
  Purchase #5 $157.68   6.558%   $168.0207   $168.02   $168.00   $168.00  
  Purchase #6 $23.28   4.207%   $24.2594   $24.26   $24.25   $24.30  
  Purchase #7 $158.31   7.772%   $170.6139   $170.61   $170.60   $170.60  
  7 purchase totals = $682.36       $732.4899   $732.48   $732.45   $732.60