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 $68.45   7.542%   $73.6125   $73.61   $73.60   $73.60  
  Purchase #2 $162.88   5.750%   $172.2456   $172.25   $172.25   $172.20  
  Purchase #3 $205.66   11.347%   $228.9962   $229.00   $229.00   $229.00  
  Purchase #4 $210.46   12.190%   $236.1151   $236.12   $236.10   $236.10  
  Purchase #5 $105.52   10.185%   $116.2672   $116.27   $116.25   $116.30  
  Purchase #6 $17.79   12.641%   $20.0388   $20.04   $20.05   $20.00  
  Purchase #7 $183.33   4.735%   $192.0107   $192.01   $192.00   $192.00  
  7 purchase totals = $954.09       $1,039.2861   $1,039.30   $1,039.25   $1,039.20