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 $71.34   3.667%   $73.956   $73.96   $73.95   $74.00  
  Purchase #2 $12.44   10.858%   $13.7907   $13.79   $13.80   $13.80  
  Purchase #3 $78.64   3.263%   $81.206   $81.21   $81.20   $81.20  
  Purchase #4 $202.64   10.296%   $223.5038   $223.50   $223.50   $223.50  
  Purchase #5 $95.50   5.237%   $100.5013   $100.50   $100.50   $100.50  
  Purchase #6 $70.93   3.459%   $73.3835   $73.38   $73.40   $73.40  
  Purchase #7 $43.33   11.146%   $48.1596   $48.16   $48.15   $48.20  
  7 purchase totals = $574.82       $614.5009   $614.50   $614.50   $614.60