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 $57.36   8.846%   $62.4341   $62.43   $62.45   $62.40  
  Purchase #2 $171.36   13.517%   $194.5227   $194.52   $194.50   $194.50  
  Purchase #3 $170.92   11.140%   $189.9605   $189.96   $189.95   $190.00  
  Purchase #4 $163.52   7.587%   $175.9263   $175.93   $175.95   $175.90  
  Purchase #5 $189.85   8.513%   $206.0119   $206.01   $206.00   $206.00  
  Purchase #6 $179.77   3.219%   $185.5568   $185.56   $185.55   $185.60  
  Purchase #7 $75.44   13.446%   $85.5837   $85.58   $85.60   $85.60  
  7 purchase totals = $1,008.22       $1,099.9960   $1,099.99   $1,100.00   $1,100.00