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 $184.71   11.605%   $206.1456   $206.15   $206.15   $206.10  
  Purchase #2 $219.58   12.367%   $246.7355   $246.74   $246.75   $246.70  
  Purchase #3 $241.56   8.732%   $262.653   $262.65   $262.65   $262.70  
  Purchase #4 $233.35   13.258%   $264.2875   $264.29   $264.30   $264.30  
  Purchase #5 $200.79   10.382%   $221.636   $221.64   $221.65   $221.60  
  Purchase #6 $235.41   8.114%   $254.5112   $254.51   $254.50   $254.50  
  Purchase #7 $60.29   11.181%   $67.031   $67.03   $67.05   $67.00  
  7 purchase totals = $1,375.69       $1,522.9998   $1,523.01   $1,523.05   $1,522.90