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 $88.60   6.806%   $94.6301   $94.63   $94.65   $94.60  
  Purchase #2 $88.44   8.835%   $96.2537   $96.25   $96.25   $96.30  
  Purchase #3 $212.74   13.583%   $241.6365   $241.64   $241.65   $241.60  
  Purchase #4 $91.42   13.135%   $103.428   $103.43   $103.45   $103.40  
  Purchase #5 $137.73   7.834%   $148.5198   $148.52   $148.50   $148.50  
  Purchase #6 $141.28   3.855%   $146.7263   $146.73   $146.75   $146.70  
  Purchase #7 $177.54   10.256%   $195.7485   $195.75   $195.75   $195.70  
  7 purchase totals = $937.75       $1,026.9429   $1,026.95   $1,027.00   $1,026.80