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 $210.46   7.178%   $225.5668   $225.57   $225.55   $225.60  
  Purchase #2 $89.43   6.426%   $95.1768   $95.18   $95.20   $95.20  
  Purchase #3 $54.80   7.161%   $58.7242   $58.72   $58.70   $58.70  
  Purchase #4 $240.97   7.209%   $258.3415   $258.34   $258.35   $258.30  
  Purchase #5 $236.83   10.663%   $262.0832   $262.08   $262.10   $262.10  
  Purchase #6 $141.92   4.647%   $148.515   $148.52   $148.50   $148.50  
  Purchase #7 $10.66   6.284%   $11.3299   $11.33   $11.35   $11.30  
  7 purchase totals = $985.07       $1,059.7374   $1,059.74   $1,059.75   $1,059.70