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 $116.45   8.334%   $126.1549   $126.15   $126.15   $126.20  
  Purchase #2 $215.96   5.499%   $227.8356   $227.84   $227.85   $227.80  
  Purchase #3 $72.95   4.490%   $76.2255   $76.23   $76.25   $76.20  
  Purchase #4 $233.84   5.301%   $246.2359   $246.24   $246.25   $246.20  
  Purchase #5 $47.55   10.570%   $52.576   $52.58   $52.60   $52.60  
  Purchase #6 $33.53   10.480%   $37.0439   $37.04   $37.05   $37.00  
  Purchase #7 $229.39   5.740%   $242.557   $242.56   $242.55   $242.60  
  7 purchase totals = $949.67       $1,008.6288   $1,008.64   $1,008.70   $1,008.60