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 $58.59   5.264%   $61.6742   $61.67   $61.65   $61.70  
  Purchase #2 $245.74   5.868%   $260.16   $260.16   $260.15   $260.20  
  Purchase #3 $34.83   12.467%   $39.1723   $39.17   $39.15   $39.20  
  Purchase #4 $69.66   6.748%   $74.3607   $74.36   $74.35   $74.40  
  Purchase #5 $49.58   5.461%   $52.2876   $52.29   $52.30   $52.30  
  Purchase #6 $93.71   4.604%   $98.0244   $98.02   $98.00   $98.00  
  Purchase #7 $108.83   6.422%   $115.8191   $115.82   $115.80   $115.80  
  7 purchase totals = $660.94       $701.4983   $701.49   $701.40   $701.60