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 $233.38   4.452%   $243.7701   $243.77   $243.75   $243.80  
  Purchase #2 $34.40   3.493%   $35.6016   $35.60   $35.60   $35.60  
  Purchase #3 $79.95   7.584%   $86.0134   $86.01   $86.00   $86.00  
  Purchase #4 $154.77   5.514%   $163.304   $163.30   $163.30   $163.30  
  Purchase #5 $229.73   3.729%   $238.2966   $238.30   $238.30   $238.30  
  Purchase #6 $117.42   12.241%   $131.7934   $131.79   $131.80   $131.80  
  Purchase #7 $167.30   5.647%   $176.7474   $176.75   $176.75   $176.70  
  7 purchase totals = $1,016.95       $1,075.5265   $1,075.52   $1,075.50   $1,075.50