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 $68.48   11.355%   $76.2559   $76.26   $76.25   $76.30  
  Purchase #2 $158.73   5.392%   $167.2887   $167.29   $167.30   $167.30  
  Purchase #3 $54.51   4.469%   $56.9461   $56.95   $56.95   $56.90  
  Purchase #4 $73.77   3.827%   $76.5932   $76.59   $76.60   $76.60  
  Purchase #5 $179.76   5.283%   $189.2567   $189.26   $189.25   $189.30  
  Purchase #6 $199.84   12.130%   $224.0806   $224.08   $224.10   $224.10  
  Purchase #7 $207.61   5.702%   $219.4479   $219.45   $219.45   $219.40  
  7 purchase totals = $942.70       $1,009.8691   $1,009.88   $1,009.90   $1,009.90