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 $67.34   8.475%   $73.0471   $73.05   $73.05   $73.00  
  Purchase #2 $123.56   6.836%   $132.0066   $132.01   $132.00   $132.00  
  Purchase #3 $217.33   7.819%   $234.323   $234.32   $234.30   $234.30  
  Purchase #4 $233.84   7.725%   $251.9041   $251.90   $251.90   $251.90  
  Purchase #5 $158.55   9.712%   $173.9484   $173.95   $173.95   $173.90  
  Purchase #6 $40.73   5.864%   $43.1184   $43.12   $43.10   $43.10  
  Purchase #7 $119.27   3.774%   $123.7712   $123.77   $123.75   $123.80  
  7 purchase totals = $960.62       $1,032.1188   $1,032.12   $1,032.05   $1,032.00