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 $62.31   5.655%   $65.8336   $65.83   $65.85   $65.80  
  Purchase #2 $247.99   7.697%   $267.0778   $267.08   $267.10   $267.10  
  Purchase #3 $78.45   10.422%   $86.6261   $86.63   $86.65   $86.60  
  Purchase #4 $219.26   12.334%   $246.3035   $246.30   $246.30   $246.30  
  Purchase #5 $250.27   4.211%   $260.8089   $260.81   $260.80   $260.80  
  Purchase #6 $24.87   12.690%   $28.026   $28.03   $28.05   $28.00  
  Purchase #7 $162.75   10.852%   $180.4116   $180.41   $180.40   $180.40  
  7 purchase totals = $1,045.90       $1,135.0875   $1,135.09   $1,135.15   $1,135.00