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 $105.25   11.414%   $117.2632   $117.26   $117.25   $117.30  
  Purchase #2 $68.94   13.783%   $78.442   $78.44   $78.45   $78.40  
  Purchase #3 $143.84   12.567%   $161.9164   $161.92   $161.90   $161.90  
  Purchase #4 $199.62   9.726%   $219.035   $219.04   $219.05   $219.00  
  Purchase #5 $230.88   4.694%   $241.7175   $241.72   $241.70   $241.70  
  Purchase #6 $37.78   10.232%   $41.6456   $41.65   $41.65   $41.60  
  Purchase #7 $228.27   3.369%   $235.9604   $235.96   $235.95   $236.00  
  7 purchase totals = $1,014.58       $1,095.9801   $1,095.99   $1,095.95   $1,095.90