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 $237.63   11.332%   $264.5582   $264.56   $264.55   $264.60  
  Purchase #2 $49.99   8.607%   $54.2926   $54.29   $54.30   $54.30  
  Purchase #3 $200.68   11.234%   $223.2244   $223.22   $223.20   $223.20  
  Purchase #4 $41.62   8.644%   $45.2176   $45.22   $45.20   $45.20  
  Purchase #5 $245.93   12.106%   $275.7023   $275.70   $275.70   $275.70  
  Purchase #6 $96.93   8.508%   $105.1768   $105.18   $105.20   $105.20  
  Purchase #7 $224.78   5.338%   $236.7788   $236.78   $236.80   $236.80  
  7 purchase totals = $1,097.56       $1,204.9507   $1,204.95   $1,204.95   $1,205.00