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 $187.38   7.626%   $201.6696   $201.67   $201.65   $201.70  
  Purchase #2 $176.25   8.557%   $191.3317   $191.33   $191.35   $191.30  
  Purchase #3 $89.88   6.287%   $95.5308   $95.53   $95.55   $95.50  
  Purchase #4 $163.88   8.457%   $177.7393   $177.74   $177.75   $177.70  
  Purchase #5 $95.98   3.331%   $99.1771   $99.18   $99.20   $99.20  
  Purchase #6 $189.25   6.665%   $201.8635   $201.86   $201.85   $201.90  
  Purchase #7 $238.37   5.740%   $252.0524   $252.05   $252.05   $252.10  
  7 purchase totals = $1,140.99       $1,219.3644   $1,219.36   $1,219.40   $1,219.40