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 $91.50   3.770%   $94.9496   $94.95   $94.95   $94.90  
  Purchase #2 $51.98   12.350%   $58.3995   $58.40   $58.40   $58.40  
  Purchase #3 $244.64   8.746%   $266.0362   $266.04   $266.05   $266.00  
  Purchase #4 $23.28   7.794%   $25.0944   $25.09   $25.10   $25.10  
  Purchase #5 $250.62   13.295%   $283.9399   $283.94   $283.95   $283.90  
  Purchase #6 $65.25   13.322%   $73.9426   $73.94   $73.95   $73.90  
  Purchase #7 $153.59   11.604%   $171.4126   $171.41   $171.40   $171.40  
  7 purchase totals = $880.86       $973.7748   $973.77   $973.80   $973.60