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 $192.99   5.764%   $204.1139   $204.11   $204.10   $204.10  
  Purchase #2 $228.37   3.777%   $236.9955   $237.00   $237.00   $237.00  
  Purchase #3 $81.41   5.122%   $85.5798   $85.58   $85.60   $85.60  
  Purchase #4 $12.30   5.808%   $13.0144   $13.01   $13.00   $13.00  
  Purchase #5 $208.40   4.274%   $217.307   $217.31   $217.30   $217.30  
  Purchase #6 $80.80   6.781%   $86.279   $86.28   $86.30   $86.30  
  Purchase #7 $211.87   7.871%   $228.5463   $228.55   $228.55   $228.50  
  7 purchase totals = $1,016.14       $1,071.8359   $1,071.84   $1,071.85   $1,071.80