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 $169.26   8.476%   $183.6065   $183.61   $183.60   $183.60  
  Purchase #2 $149.28   7.645%   $160.6925   $160.69   $160.70   $160.70  
  Purchase #3 $64.27   10.789%   $71.2041   $71.20   $71.20   $71.20  
  Purchase #4 $123.80   7.765%   $133.4131   $133.41   $133.40   $133.40  
  Purchase #5 $163.28   8.783%   $177.6209   $177.62   $177.60   $177.60  
  Purchase #6 $13.52   11.561%   $15.083   $15.08   $15.10   $15.10  
  Purchase #7 $17.55   11.711%   $19.6053   $19.61   $19.60   $19.60  
  7 purchase totals = $700.96       $761.2254   $761.22   $761.20   $761.20