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 $187.30   7.775%   $201.8626   $201.86   $201.85   $201.90  
  Purchase #2 $174.61   11.334%   $194.4003   $194.40   $194.40   $194.40  
  Purchase #3 $175.79   11.455%   $195.9267   $195.93   $195.95   $195.90  
  Purchase #4 $58.79   9.590%   $64.428   $64.43   $64.45   $64.40  
  Purchase #5 $25.72   3.529%   $26.6277   $26.63   $26.65   $26.60  
  Purchase #6 $207.49   7.560%   $223.1762   $223.18   $223.20   $223.20  
  Purchase #7 $166.56   3.140%   $171.79   $171.79   $171.80   $171.80  
  7 purchase totals = $996.26       $1,078.2115   $1,078.22   $1,078.30   $1,078.20