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 $85.53   11.447%   $95.3206   $95.32   $95.30   $95.30  
  Purchase #2 $248.78   9.209%   $271.6902   $271.69   $271.70   $271.70  
  Purchase #3 $220.27   7.742%   $237.3233   $237.32   $237.30   $237.30  
  Purchase #4 $86.55   11.273%   $96.3068   $96.31   $96.30   $96.30  
  Purchase #5 $235.35   10.531%   $260.1347   $260.13   $260.15   $260.10  
  Purchase #6 $103.45   11.761%   $115.6168   $115.62   $115.60   $115.60  
  Purchase #7 $204.31   10.710%   $226.1916   $226.19   $226.20   $226.20  
  7 purchase totals = $1,184.24       $1,302.5840   $1,302.58   $1,302.55   $1,302.50