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 $191.67   10.741%   $212.2573   $212.26   $212.25   $212.30  
  Purchase #2 $233.74   8.488%   $253.5799   $253.58   $253.60   $253.60  
  Purchase #3 $12.60   9.788%   $13.8333   $13.83   $13.85   $13.80  
  Purchase #4 $169.40   7.130%   $181.4782   $181.48   $181.50   $181.50  
  Purchase #5 $234.61   5.712%   $248.0109   $248.01   $248.00   $248.00  
  Purchase #6 $69.33   10.252%   $76.4377   $76.44   $76.45   $76.40  
  Purchase #7 $91.86   5.578%   $96.984   $96.98   $97.00   $97.00  
  7 purchase totals = $1,003.21       $1,082.5813   $1,082.58   $1,082.65   $1,082.60