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 $196.60   13.873%   $223.8743   $223.87   $223.85   $223.90  
  Purchase #2 $178.85   8.208%   $193.53   $193.53   $193.55   $193.50  
  Purchase #3 $166.79   5.701%   $176.2987   $176.30   $176.30   $176.30  
  Purchase #4 $113.97   11.247%   $126.7882   $126.79   $126.80   $126.80  
  Purchase #5 $55.50   11.503%   $61.8842   $61.88   $61.90   $61.90  
  Purchase #6 $36.43   4.559%   $38.0908   $38.09   $38.10   $38.10  
  Purchase #7 $223.86   8.586%   $243.0806   $243.08   $243.10   $243.10  
  7 purchase totals = $972.00       $1,063.5468   $1,063.54   $1,063.60   $1,063.60