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 $69.43   11.732%   $77.5755   $77.58   $77.60   $77.60  
  Purchase #2 $99.37   11.103%   $110.4031   $110.40   $110.40   $110.40  
  Purchase #3 $53.50   13.282%   $60.6059   $60.61   $60.60   $60.60  
  Purchase #4 $135.38   5.472%   $142.788   $142.79   $142.80   $142.80  
  Purchase #5 $231.43   13.520%   $262.7193   $262.72   $262.70   $262.70  
  Purchase #6 $185.49   10.183%   $204.3784   $204.38   $204.40   $204.40  
  Purchase #7 $161.83   9.442%   $177.11   $177.11   $177.10   $177.10  
  7 purchase totals = $936.43       $1,035.5802   $1,035.59   $1,035.60   $1,035.60