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 $196.42   5.670%   $207.557   $207.56   $207.55   $207.60  
  Purchase #2 $250.26   13.420%   $283.8449   $283.84   $283.85   $283.80  
  Purchase #3 $160.69   3.383%   $166.1261   $166.13   $166.15   $166.10  
  Purchase #4 $141.88   12.283%   $159.3071   $159.31   $159.30   $159.30  
  Purchase #5 $235.67   8.609%   $255.9588   $255.96   $255.95   $256.00  
  Purchase #6 $182.68   13.738%   $207.7766   $207.78   $207.80   $207.80  
  Purchase #7 $217.34   12.671%   $244.8792   $244.88   $244.90   $244.90  
  7 purchase totals = $1,384.94       $1,525.4497   $1,525.46   $1,525.50   $1,525.50