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 $192.37   4.512%   $201.0497   $201.05   $201.05   $201.00  
  Purchase #2 $59.53   5.252%   $62.6565   $62.66   $62.65   $62.70  
  Purchase #3 $110.71   6.121%   $117.4866   $117.49   $117.50   $117.50  
  Purchase #4 $63.30   11.505%   $70.5827   $70.58   $70.60   $70.60  
  Purchase #5 $249.88   13.597%   $283.8562   $283.86   $283.85   $283.90  
  Purchase #6 $182.58   5.802%   $193.1733   $193.17   $193.15   $193.20  
  Purchase #7 $163.62   11.554%   $182.5247   $182.52   $182.50   $182.50  
  7 purchase totals = $1,021.99       $1,111.3297   $1,111.33   $1,111.30   $1,111.40