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 $161.95   11.540%   $180.639   $180.64   $180.65   $180.60  
  Purchase #2 $10.71   11.549%   $11.9469   $11.95   $11.95   $11.90  
  Purchase #3 $217.98   10.865%   $241.6635   $241.66   $241.65   $241.70  
  Purchase #4 $151.75   11.622%   $169.3864   $169.39   $169.40   $169.40  
  Purchase #5 $32.30   7.325%   $34.666   $34.67   $34.65   $34.70  
  Purchase #6 $215.76   7.213%   $231.3228   $231.32   $231.30   $231.30  
  Purchase #7 $183.35   5.645%   $193.7001   $193.70   $193.70   $193.70  
  7 purchase totals = $973.80       $1,063.3247   $1,063.33   $1,063.30   $1,063.30