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 $71.86   5.808%   $76.0336   $76.03   $76.05   $76.00  
  Purchase #2 $109.31   12.461%   $122.9311   $122.93   $122.95   $122.90  
  Purchase #3 $59.88   7.505%   $64.374   $64.37   $64.35   $64.40  
  Purchase #4 $237.80   10.409%   $262.5526   $262.55   $262.55   $262.60  
  Purchase #5 $235.71   3.283%   $243.4484   $243.45   $243.45   $243.40  
  Purchase #6 $250.46   9.657%   $274.6469   $274.65   $274.65   $274.60  
  Purchase #7 $222.39   4.120%   $231.5525   $231.55   $231.55   $231.60  
  7 purchase totals = $1,187.41       $1,275.5391   $1,275.53   $1,275.55   $1,275.50