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 $142.67   7.558%   $153.453   $153.45   $153.45   $153.50  
  Purchase #2 $183.27   5.770%   $193.8447   $193.84   $193.85   $193.80  
  Purchase #3 $146.28   3.496%   $151.3939   $151.39   $151.40   $151.40  
  Purchase #4 $15.86   7.502%   $17.0498   $17.05   $17.05   $17.00  
  Purchase #5 $175.89   8.818%   $191.4   $191.40   $191.40   $191.40  
  Purchase #6 $155.56   13.233%   $176.1453   $176.15   $176.15   $176.10  
  Purchase #7 $244.63   8.254%   $264.8218   $264.82   $264.80   $264.80  
  7 purchase totals = $1,064.16       $1,148.1085   $1,148.10   $1,148.10   $1,148.00