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 $86.97   7.672%   $93.6423   $93.64   $93.65   $93.60  
  Purchase #2 $157.70   3.703%   $163.5396   $163.54   $163.55   $163.50  
  Purchase #3 $117.47   11.321%   $130.7688   $130.77   $130.75   $130.80  
  Purchase #4 $97.94   11.363%   $109.0689   $109.07   $109.05   $109.10  
  Purchase #5 $108.26   13.434%   $122.8036   $122.80   $122.80   $122.80  
  Purchase #6 $169.83   6.839%   $181.4447   $181.44   $181.45   $181.40  
  Purchase #7 $238.67   11.492%   $266.098   $266.10   $266.10   $266.10  
  7 purchase totals = $976.84       $1,067.3659   $1,067.36   $1,067.35   $1,067.30