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 $47.58   4.733%   $49.832   $49.83   $49.85   $49.80  
  Purchase #2 $221.98   10.801%   $245.9561   $245.96   $245.95   $246.00  
  Purchase #3 $219.57   10.478%   $242.5765   $242.58   $242.60   $242.60  
  Purchase #4 $206.38   3.440%   $213.4795   $213.48   $213.50   $213.50  
  Purchase #5 $85.52   10.828%   $94.7801   $94.78   $94.80   $94.80  
  Purchase #6 $181.37   10.321%   $200.0892   $200.09   $200.10   $200.10  
  Purchase #7 $106.25   10.301%   $117.1948   $117.19   $117.20   $117.20  
  7 purchase totals = $1,068.65       $1,163.9082   $1,163.91   $1,164.00   $1,164.00