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 $199.98   4.344%   $208.6671   $208.67   $208.65   $208.70  
  Purchase #2 $216.53   6.492%   $230.5871   $230.59   $230.60   $230.60  
  Purchase #3 $225.54   8.578%   $244.8868   $244.89   $244.90   $244.90  
  Purchase #4 $58.37   3.656%   $60.504   $60.50   $60.50   $60.50  
  Purchase #5 $236.44   3.152%   $243.8926   $243.89   $243.90   $243.90  
  Purchase #6 $147.50   4.412%   $154.0077   $154.01   $154.00   $154.00  
  Purchase #7 $238.50   8.648%   $259.1255   $259.13   $259.15   $259.10  
  7 purchase totals = $1,322.86       $1,401.6708   $1,401.68   $1,401.70   $1,401.70