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 $125.26   8.233%   $135.5727   $135.57   $135.55   $135.60  
  Purchase #2 $240.70   5.607%   $254.196   $254.20   $254.20   $254.20  
  Purchase #3 $166.84   11.687%   $186.3386   $186.34   $186.35   $186.30  
  Purchase #4 $24.49   8.186%   $26.4948   $26.49   $26.50   $26.50  
  Purchase #5 $149.89   9.124%   $163.566   $163.57   $163.55   $163.60  
  Purchase #6 $102.69   8.851%   $111.7791   $111.78   $111.80   $111.80  
  Purchase #7 $230.98   6.743%   $246.555   $246.56   $246.55   $246.60  
  7 purchase totals = $1,040.85       $1,124.5022   $1,124.51   $1,124.50   $1,124.60