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 $44.84   8.522%   $48.6613   $48.66   $48.65   $48.70  
  Purchase #2 $67.68   11.165%   $75.2365   $75.24   $75.25   $75.20  
  Purchase #3 $183.44   11.650%   $204.8108   $204.81   $204.80   $204.80  
  Purchase #4 $249.82   7.703%   $269.0636   $269.06   $269.05   $269.10  
  Purchase #5 $199.55   3.571%   $206.6759   $206.68   $206.70   $206.70  
  Purchase #6 $157.48   7.543%   $169.3587   $169.36   $169.35   $169.40  
  Purchase #7 $236.41   9.351%   $258.5167   $258.52   $258.50   $258.50  
  7 purchase totals = $1,139.22       $1,232.3235   $1,232.33   $1,232.30   $1,232.40