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 $183.68   10.789%   $203.4972   $203.50   $203.50   $203.50  
  Purchase #2 $165.61   8.299%   $179.354   $179.35   $179.35   $179.40  
  Purchase #3 $132.58   8.388%   $143.7008   $143.70   $143.70   $143.70  
  Purchase #4 $108.52   7.326%   $116.4702   $116.47   $116.45   $116.50  
  Purchase #5 $169.93   10.416%   $187.6299   $187.63   $187.65   $187.60  
  Purchase #6 $195.55   5.258%   $205.832   $205.83   $205.85   $205.80  
  Purchase #7 $166.26   3.426%   $171.9561   $171.96   $171.95   $172.00  
  7 purchase totals = $1,122.13       $1,208.4402   $1,208.44   $1,208.45   $1,208.50