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 $184.30   5.183%   $193.8523   $193.85   $193.85   $193.90  
  Purchase #2 $63.54   7.483%   $68.2947   $68.29   $68.30   $68.30  
  Purchase #3 $159.30   10.837%   $176.5633   $176.56   $176.55   $176.60  
  Purchase #4 $67.46   8.617%   $73.273   $73.27   $73.25   $73.30  
  Purchase #5 $214.52   13.771%   $244.0615   $244.06   $244.05   $244.10  
  Purchase #6 $224.53   3.327%   $232.0001   $232.00   $232.00   $232.00  
  Purchase #7 $12.89   4.818%   $13.511   $13.51   $13.50   $13.50  
  7 purchase totals = $926.54       $1,001.5559   $1,001.54   $1,001.50   $1,001.70