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 $42.38   3.647%   $43.9256   $43.93   $43.95   $43.90  
  Purchase #2 $128.84   7.373%   $138.3394   $138.34   $138.35   $138.30  
  Purchase #3 $144.96   5.579%   $153.0473   $153.05   $153.05   $153.00  
  Purchase #4 $67.31   4.838%   $70.5665   $70.57   $70.55   $70.60  
  Purchase #5 $206.95   13.208%   $234.284   $234.28   $234.30   $234.30  
  Purchase #6 $112.62   6.642%   $120.1002   $120.10   $120.10   $120.10  
  Purchase #7 $196.91   5.752%   $208.2363   $208.24   $208.25   $208.20  
  7 purchase totals = $899.97       $968.4993   $968.51   $968.55   $968.40