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 $58.28   4.619%   $60.972   $60.97   $60.95   $61.00  
  Purchase #2 $60.26   7.729%   $64.9175   $64.92   $64.90   $64.90  
  Purchase #3 $224.61   10.761%   $248.7803   $248.78   $248.80   $248.80  
  Purchase #4 $208.35   9.386%   $227.9057   $227.91   $227.90   $227.90  
  Purchase #5 $213.73   6.108%   $226.7846   $226.78   $226.80   $226.80  
  Purchase #6 $228.95   11.313%   $254.8511   $254.85   $254.85   $254.90  
  Purchase #7 $129.39   7.772%   $139.4462   $139.45   $139.45   $139.40  
  7 purchase totals = $1,123.57       $1,223.6574   $1,223.66   $1,223.65   $1,223.70