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 $194.99   5.491%   $205.6969   $205.70   $205.70   $205.70  
  Purchase #2 $181.41   12.755%   $204.5488   $204.55   $204.55   $204.50  
  Purchase #3 $153.84   6.308%   $163.5442   $163.54   $163.55   $163.50  
  Purchase #4 $11.96   10.607%   $13.2286   $13.23   $13.25   $13.20  
  Purchase #5 $38.49   3.145%   $39.7005   $39.70   $39.70   $39.70  
  Purchase #6 $186.88   5.859%   $197.8293   $197.83   $197.85   $197.80  
  Purchase #7 $177.32   12.424%   $199.3502   $199.35   $199.35   $199.40  
  7 purchase totals = $944.89       $1,023.8985   $1,023.90   $1,023.95   $1,023.80