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 $59.68   4.547%   $62.3936   $62.39   $62.40   $62.40  
  Purchase #2 $49.82   5.534%   $52.577   $52.58   $52.60   $52.60  
  Purchase #3 $168.96   3.713%   $175.2335   $175.23   $175.25   $175.20  
  Purchase #4 $184.25   6.734%   $196.6574   $196.66   $196.65   $196.70  
  Purchase #5 $227.29   10.303%   $250.7077   $250.71   $250.70   $250.70  
  Purchase #6 $196.78   3.816%   $204.2891   $204.29   $204.30   $204.30  
  Purchase #7 $219.41   10.312%   $242.0356   $242.04   $242.05   $242.00  
  7 purchase totals = $1,106.19       $1,183.8939   $1,183.90   $1,183.95   $1,183.90