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 $114.41   10.541%   $126.47   $126.47   $126.45   $126.50  
  Purchase #2 $91.35   7.746%   $98.426   $98.43   $98.45   $98.40  
  Purchase #3 $144.57   8.102%   $156.2831   $156.28   $156.30   $156.30  
  Purchase #4 $181.95   10.827%   $201.6497   $201.65   $201.65   $201.60  
  Purchase #5 $49.68   7.765%   $53.5377   $53.54   $53.55   $53.50  
  Purchase #6 $156.93   12.485%   $176.5227   $176.52   $176.50   $176.50  
  Purchase #7 $11.99   4.484%   $12.5276   $12.53   $12.55   $12.50  
  7 purchase totals = $750.88       $825.4168   $825.42   $825.45   $825.30