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 $162.69   7.587%   $175.0333   $175.03   $175.05   $175.00  
  Purchase #2 $70.74   6.433%   $75.2907   $75.29   $75.30   $75.30  
  Purchase #3 $222.86   6.635%   $237.6468   $237.65   $237.65   $237.60  
  Purchase #4 $170.72   11.325%   $190.054   $190.05   $190.05   $190.10  
  Purchase #5 $107.70   10.541%   $119.0527   $119.05   $119.05   $119.10  
  Purchase #6 $113.63   11.711%   $126.9372   $126.94   $126.95   $126.90  
  Purchase #7 $116.76   11.666%   $130.3812   $130.38   $130.40   $130.40  
  7 purchase totals = $965.10       $1,054.3959   $1,054.39   $1,054.45   $1,054.40