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 $182.65   10.770%   $202.3214   $202.32   $202.30   $202.30  
  Purchase #2 $146.57   13.667%   $166.6017   $166.60   $166.60   $166.60  
  Purchase #3 $124.73   7.293%   $133.8266   $133.83   $133.85   $133.80  
  Purchase #4 $45.64   13.159%   $51.6458   $51.65   $51.65   $51.60  
  Purchase #5 $161.54   11.404%   $179.962   $179.96   $179.95   $180.00  
  Purchase #6 $172.37   13.770%   $196.1053   $196.11   $196.10   $196.10  
  Purchase #7 $175.59   11.229%   $195.307   $195.31   $195.30   $195.30  
  7 purchase totals = $1,009.09       $1,125.7698   $1,125.78   $1,125.75   $1,125.70