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 $23.81   11.451%   $26.5365   $26.54   $26.55   $26.50  
  Purchase #2 $211.29   11.365%   $235.3031   $235.30   $235.30   $235.30  
  Purchase #3 $71.80   7.819%   $77.414   $77.41   $77.40   $77.40  
  Purchase #4 $167.74   4.171%   $174.7364   $174.74   $174.75   $174.70  
  Purchase #5 $37.91   3.751%   $39.332   $39.33   $39.35   $39.30  
  Purchase #6 $206.32   13.521%   $234.2165   $234.22   $234.20   $234.20  
  Purchase #7 $196.48   13.710%   $223.4174   $223.42   $223.40   $223.40  
  7 purchase totals = $915.35       $1,010.9559   $1,010.96   $1,010.95   $1,010.80