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 $94.70   3.422%   $97.9406   $97.94   $97.95   $97.90  
  Purchase #2 $191.46   9.136%   $208.9518   $208.95   $208.95   $209.00  
  Purchase #3 $227.72   5.752%   $240.8185   $240.82   $240.80   $240.80  
  Purchase #4 $223.66   5.632%   $236.2565   $236.26   $236.25   $236.30  
  Purchase #5 $86.33   13.133%   $97.6677   $97.67   $97.65   $97.70  
  Purchase #6 $206.46   7.427%   $221.7938   $221.79   $221.80   $221.80  
  Purchase #7 $74.39   8.318%   $80.5778   $80.58   $80.60   $80.60  
  7 purchase totals = $1,104.72       $1,184.0067   $1,184.01   $1,184.00   $1,184.10