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 $180.55   8.293%   $195.523   $195.52   $195.50   $195.50  
  Purchase #2 $84.52   9.405%   $92.4691   $92.47   $92.45   $92.50  
  Purchase #3 $122.25   12.544%   $137.585   $137.59   $137.60   $137.60  
  Purchase #4 $143.74   7.393%   $154.3667   $154.37   $154.35   $154.40  
  Purchase #5 $222.28   6.539%   $236.8149   $236.81   $236.80   $236.80  
  Purchase #6 $187.32   4.331%   $195.4328   $195.43   $195.45   $195.40  
  Purchase #7 $235.65   6.585%   $251.1676   $251.17   $251.15   $251.20  
  7 purchase totals = $1,176.31       $1,263.3591   $1,263.36   $1,263.30   $1,263.40