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 $36.38   3.487%   $37.6486   $37.65   $37.65   $37.60  
  Purchase #2 $54.81   13.158%   $62.0219   $62.02   $62.00   $62.00  
  Purchase #3 $192.66   10.239%   $212.3865   $212.39   $212.40   $212.40  
  Purchase #4 $237.85   6.387%   $253.0415   $253.04   $253.05   $253.00  
  Purchase #5 $105.45   7.144%   $112.9833   $112.98   $113.00   $113.00  
  Purchase #6 $112.35   9.378%   $122.8862   $122.89   $122.90   $122.90  
  Purchase #7 $83.61   13.136%   $94.593   $94.59   $94.60   $94.60  
  7 purchase totals = $823.11       $895.5610   $895.56   $895.60   $895.50