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 $58.32   5.857%   $61.7358   $61.74   $61.75   $61.70  
  Purchase #2 $234.40   13.292%   $265.5564   $265.56   $265.55   $265.60  
  Purchase #3 $178.40   9.557%   $195.4497   $195.45   $195.45   $195.40  
  Purchase #4 $172.28   3.208%   $177.8067   $177.81   $177.80   $177.80  
  Purchase #5 $168.98   13.286%   $191.4307   $191.43   $191.45   $191.40  
  Purchase #6 $99.69   11.245%   $110.9001   $110.90   $110.90   $110.90  
  Purchase #7 $192.57   3.441%   $199.1963   $199.20   $199.20   $199.20  
  7 purchase totals = $1,104.64       $1,202.0757   $1,202.09   $1,202.10   $1,202.00