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 $149.66   3.416%   $154.7724   $154.77   $154.75   $154.80  
  Purchase #2 $240.99   11.628%   $269.0123   $269.01   $269.00   $269.00  
  Purchase #3 $236.74   9.574%   $259.4055   $259.41   $259.40   $259.40  
  Purchase #4 $64.43   11.235%   $71.6687   $71.67   $71.65   $71.70  
  Purchase #5 $160.71   7.683%   $173.0573   $173.06   $173.05   $173.10  
  Purchase #6 $129.32   9.308%   $141.3571   $141.36   $141.35   $141.40  
  Purchase #7 $83.51   10.150%   $91.9863   $91.99   $92.00   $92.00  
  7 purchase totals = $1,065.36       $1,161.2596   $1,161.27   $1,161.20   $1,161.40