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 $193.94   5.806%   $205.2002   $205.20   $205.20   $205.20  
  Purchase #2 $99.31   11.803%   $111.0316   $111.03   $111.05   $111.00  
  Purchase #3 $250.56   8.706%   $272.3738   $272.37   $272.35   $272.40  
  Purchase #4 $51.97   3.355%   $53.7136   $53.71   $53.70   $53.70  
  Purchase #5 $191.34   3.438%   $197.9183   $197.92   $197.90   $197.90  
  Purchase #6 $181.28   9.141%   $197.8508   $197.85   $197.85   $197.90  
  Purchase #7 $64.65   6.485%   $68.8426   $68.84   $68.85   $68.80  
  7 purchase totals = $1,033.05       $1,106.9309   $1,106.92   $1,106.90   $1,106.90