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 $69.76   9.442%   $76.3467   $76.35   $76.35   $76.30  
  Purchase #2 $213.68   10.436%   $235.9796   $235.98   $236.00   $236.00  
  Purchase #3 $50.29   4.627%   $52.6169   $52.62   $52.60   $52.60  
  Purchase #4 $197.64   11.527%   $220.422   $220.42   $220.40   $220.40  
  Purchase #5 $159.68   8.433%   $173.1458   $173.15   $173.15   $173.10  
  Purchase #6 $154.60   5.806%   $163.5761   $163.58   $163.60   $163.60  
  Purchase #7 $210.93   10.507%   $233.0924   $233.09   $233.10   $233.10  
  7 purchase totals = $1,056.58       $1,155.1795   $1,155.19   $1,155.20   $1,155.10