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 $184.91   5.464%   $195.0135   $195.01   $195.00   $195.00  
  Purchase #2 $68.74   7.760%   $74.0742   $74.07   $74.05   $74.10  
  Purchase #3 $115.79   6.682%   $123.5271   $123.53   $123.55   $123.50  
  Purchase #4 $103.65   3.126%   $106.8901   $106.89   $106.90   $106.90  
  Purchase #5 $163.46   12.687%   $184.1982   $184.20   $184.20   $184.20  
  Purchase #6 $54.52   11.714%   $60.9065   $60.91   $60.90   $60.90  
  Purchase #7 $70.32   11.332%   $78.2887   $78.29   $78.30   $78.30  
  7 purchase totals = $761.39       $822.8983   $822.90   $822.90   $822.90