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 $173.47   4.523%   $181.316   $181.32   $181.30   $181.30  
  Purchase #2 $221.49   8.843%   $241.0764   $241.08   $241.10   $241.10  
  Purchase #3 $173.74   5.859%   $183.9194   $183.92   $183.90   $183.90  
  Purchase #4 $58.77   11.421%   $65.4821   $65.48   $65.50   $65.50  
  Purchase #5 $207.98   3.621%   $215.511   $215.51   $215.50   $215.50  
  Purchase #6 $146.48   5.405%   $154.3972   $154.40   $154.40   $154.40  
  Purchase #7 $116.41   8.206%   $125.9626   $125.96   $125.95   $126.00  
  7 purchase totals = $1,098.34       $1,167.6647   $1,167.67   $1,167.65   $1,167.70