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 $182.47   8.562%   $198.0931   $198.09   $198.10   $198.10  
  Purchase #2 $87.38   11.756%   $97.6524   $97.65   $97.65   $97.70  
  Purchase #3 $53.58   13.415%   $60.7678   $60.77   $60.75   $60.80  
  Purchase #4 $215.92   10.595%   $238.7967   $238.80   $238.80   $238.80  
  Purchase #5 $165.83   7.874%   $178.8875   $178.89   $178.90   $178.90  
  Purchase #6 $177.59   9.190%   $193.9105   $193.91   $193.90   $193.90  
  Purchase #7 $188.38   3.285%   $194.5683   $194.57   $194.55   $194.60  
  7 purchase totals = $1,071.15       $1,162.6763   $1,162.68   $1,162.65   $1,162.80