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 $119.89   5.391%   $126.3533   $126.35   $126.35   $126.40  
  Purchase #2 $153.76   13.598%   $174.6683   $174.67   $174.65   $174.70  
  Purchase #3 $20.44   12.290%   $22.9521   $22.95   $22.95   $23.00  
  Purchase #4 $170.96   4.429%   $178.5318   $178.53   $178.55   $178.50  
  Purchase #5 $230.59   9.400%   $252.2655   $252.27   $252.25   $252.30  
  Purchase #6 $130.36   10.665%   $144.2629   $144.26   $144.25   $144.30  
  Purchase #7 $130.98   12.367%   $147.1783   $147.18   $147.20   $147.20  
  7 purchase totals = $956.98       $1,046.2122   $1,046.21   $1,046.20   $1,046.40