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 $61.99   5.335%   $65.2972   $65.30   $65.30   $65.30  
  Purchase #2 $211.90   3.161%   $218.5982   $218.60   $218.60   $218.60  
  Purchase #3 $82.50   6.723%   $88.0465   $88.05   $88.05   $88.00  
  Purchase #4 $133.35   12.145%   $149.5454   $149.55   $149.55   $149.50  
  Purchase #5 $25.30   7.637%   $27.2322   $27.23   $27.25   $27.20  
  Purchase #6 $78.37   5.850%   $82.9546   $82.95   $82.95   $83.00  
  Purchase #7 $229.86   5.244%   $241.9139   $241.91   $241.90   $241.90  
  7 purchase totals = $823.27       $873.5880   $873.59   $873.60   $873.50