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 $69.27   13.468%   $78.5993   $78.60   $78.60   $78.60  
  Purchase #2 $199.38   9.822%   $218.9631   $218.96   $218.95   $219.00  
  Purchase #3 $22.98   7.406%   $24.6819   $24.68   $24.70   $24.70  
  Purchase #4 $59.69   6.356%   $63.4839   $63.48   $63.50   $63.50  
  Purchase #5 $167.40   11.177%   $186.1103   $186.11   $186.10   $186.10  
  Purchase #6 $130.54   4.790%   $136.7929   $136.79   $136.80   $136.80  
  Purchase #7 $136.57   9.523%   $149.5756   $149.58   $149.60   $149.60  
  7 purchase totals = $785.83       $858.2070   $858.20   $858.25   $858.30