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 $186.41   8.337%   $201.951   $201.95   $201.95   $202.00  
  Purchase #2 $243.29   4.166%   $253.4255   $253.43   $253.45   $253.40  
  Purchase #3 $151.83   7.103%   $162.6145   $162.61   $162.60   $162.60  
  Purchase #4 $214.71   9.207%   $234.4783   $234.48   $234.50   $234.50  
  Purchase #5 $235.56   10.621%   $260.5788   $260.58   $260.60   $260.60  
  Purchase #6 $174.27   7.488%   $187.3193   $187.32   $187.30   $187.30  
  Purchase #7 $106.89   8.265%   $115.7245   $115.72   $115.70   $115.70  
  7 purchase totals = $1,312.96       $1,416.0919   $1,416.09   $1,416.10   $1,416.10