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 $61.81   3.176%   $63.7731   $63.77   $63.75   $63.80  
  Purchase #2 $156.73   7.749%   $168.875   $168.88   $168.90   $168.90  
  Purchase #3 $242.80   9.793%   $266.5774   $266.58   $266.60   $266.60  
  Purchase #4 $160.31   12.470%   $180.3007   $180.30   $180.30   $180.30  
  Purchase #5 $238.25   9.434%   $260.7265   $260.73   $260.75   $260.70  
  Purchase #6 $172.44   12.506%   $194.0053   $194.01   $194.00   $194.00  
  Purchase #7 $38.75   7.667%   $41.721   $41.72   $41.70   $41.70  
  7 purchase totals = $1,071.09       $1,175.9790   $1,175.99   $1,176.00   $1,176.00