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 $87.52   9.248%   $95.6138   $95.61   $95.60   $95.60  
  Purchase #2 $185.84   12.544%   $209.1518   $209.15   $209.15   $209.20  
  Purchase #3 $35.99   7.565%   $38.7126   $38.71   $38.70   $38.70  
  Purchase #4 $30.73   7.794%   $33.1251   $33.13   $33.15   $33.10  
  Purchase #5 $219.52   7.514%   $236.0147   $236.01   $236.00   $236.00  
  Purchase #6 $200.74   4.248%   $209.2674   $209.27   $209.25   $209.30  
  Purchase #7 $115.68   4.684%   $121.0985   $121.10   $121.10   $121.10  
  7 purchase totals = $876.02       $942.9839   $942.98   $942.95   $943.00