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 $62.81   13.864%   $71.518   $71.52   $71.50   $71.50  
  Purchase #2 $228.29   12.858%   $257.6435   $257.64   $257.65   $257.60  
  Purchase #3 $188.63   7.640%   $203.0413   $203.04   $203.05   $203.00  
  Purchase #4 $143.42   11.655%   $160.1356   $160.14   $160.15   $160.10  
  Purchase #5 $73.42   12.483%   $82.585   $82.59   $82.60   $82.60  
  Purchase #6 $214.36   8.865%   $233.363   $233.36   $233.35   $233.40  
  Purchase #7 $140.85   11.499%   $157.0463   $157.05   $157.05   $157.00  
  7 purchase totals = $1,051.78       $1,165.3327   $1,165.34   $1,165.35   $1,165.20