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 $84.26   13.265%   $95.4371   $95.44   $95.45   $95.40  
  Purchase #2 $196.26   5.232%   $206.5283   $206.53   $206.55   $206.50  
  Purchase #3 $229.45   12.509%   $258.1519   $258.15   $258.15   $258.20  
  Purchase #4 $112.39   10.402%   $124.0808   $124.08   $124.10   $124.10  
  Purchase #5 $165.71   6.857%   $177.0727   $177.07   $177.05   $177.10  
  Purchase #6 $85.37   3.145%   $88.0549   $88.05   $88.05   $88.10  
  Purchase #7 $130.28   12.813%   $146.9728   $146.97   $146.95   $147.00  
  7 purchase totals = $1,003.72       $1,096.2985   $1,096.29   $1,096.30   $1,096.40