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 $54.58   9.224%   $59.6145   $59.61   $59.60   $59.60  
  Purchase #2 $241.67   8.462%   $262.1201   $262.12   $262.10   $262.10  
  Purchase #3 $249.37   10.790%   $276.277   $276.28   $276.30   $276.30  
  Purchase #4 $66.88   6.208%   $71.0319   $71.03   $71.05   $71.00  
  Purchase #5 $155.75   13.847%   $177.3167   $177.32   $177.30   $177.30  
  Purchase #6 $142.68   9.545%   $156.2988   $156.30   $156.30   $156.30  
  Purchase #7 $146.40   10.561%   $161.8613   $161.86   $161.85   $161.90  
  7 purchase totals = $1,057.33       $1,164.5203   $1,164.52   $1,164.50   $1,164.50