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 $60.25   9.548%   $66.0027   $66.00   $66.00   $66.00  
  Purchase #2 $233.80   9.119%   $255.1202   $255.12   $255.10   $255.10  
  Purchase #3 $12.53   12.246%   $14.0644   $14.06   $14.05   $14.10  
  Purchase #4 $58.85   11.778%   $65.7814   $65.78   $65.80   $65.80  
  Purchase #5 $195.82   8.254%   $211.983   $211.98   $212.00   $212.00  
  Purchase #6 $66.42   7.723%   $71.5496   $71.55   $71.55   $71.50  
  Purchase #7 $230.56   7.128%   $246.9943   $246.99   $247.00   $247.00  
  7 purchase totals = $858.23       $931.4956   $931.48   $931.50   $931.50