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 $60.35   13.818%   $68.6892   $68.69   $68.70   $68.70  
  Purchase #2 $134.29   11.493%   $149.7239   $149.72   $149.70   $149.70  
  Purchase #3 $123.92   6.480%   $131.95   $131.95   $131.95   $132.00  
  Purchase #4 $188.58   9.640%   $206.7591   $206.76   $206.75   $206.80  
  Purchase #5 $235.72   11.741%   $263.3959   $263.40   $263.40   $263.40  
  Purchase #6 $123.63   4.250%   $128.8843   $128.88   $128.90   $128.90  
  Purchase #7 $68.93   9.649%   $75.5811   $75.58   $75.60   $75.60  
  7 purchase totals = $935.42       $1,024.9835   $1,024.98   $1,025.00   $1,025.10