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 $97.58   9.566%   $106.9145   $106.91   $106.90   $106.90  
  Purchase #2 $137.94   13.819%   $157.0019   $157.00   $157.00   $157.00  
  Purchase #3 $164.39   8.738%   $178.7544   $178.75   $178.75   $178.80  
  Purchase #4 $24.69   11.261%   $27.4703   $27.47   $27.45   $27.50  
  Purchase #5 $209.72   3.307%   $216.6554   $216.66   $216.65   $216.70  
  Purchase #6 $241.91   10.601%   $267.5549   $267.55   $267.55   $267.60  
  Purchase #7 $93.51   5.123%   $98.3005   $98.30   $98.30   $98.30  
  7 purchase totals = $969.74       $1,052.6519   $1,052.64   $1,052.60   $1,052.80