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 $160.60   12.562%   $180.7746   $180.77   $180.75   $180.80  
  Purchase #2 $172.50   12.775%   $194.5369   $194.54   $194.55   $194.50  
  Purchase #3 $38.55   12.236%   $43.267   $43.27   $43.25   $43.30  
  Purchase #4 $239.91   13.296%   $271.8084   $271.81   $271.80   $271.80  
  Purchase #5 $121.56   4.156%   $126.612   $126.61   $126.60   $126.60  
  Purchase #6 $159.86   10.309%   $176.34   $176.34   $176.35   $176.30  
  Purchase #7 $167.64   4.113%   $174.535   $174.54   $174.55   $174.50  
  7 purchase totals = $1,060.62       $1,167.8739   $1,167.88   $1,167.85   $1,167.80