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 $23.28   7.226%   $24.9622   $24.96   $24.95   $25.00  
  Purchase #2 $248.98   10.471%   $275.0507   $275.05   $275.05   $275.10  
  Purchase #3 $234.56   5.211%   $246.7829   $246.78   $246.80   $246.80  
  Purchase #4 $244.43   5.221%   $257.1917   $257.19   $257.20   $257.20  
  Purchase #5 $159.74   8.717%   $173.6645   $173.66   $173.65   $173.70  
  Purchase #6 $147.27   11.163%   $163.7098   $163.71   $163.70   $163.70  
  Purchase #7 $114.41   10.324%   $126.2217   $126.22   $126.20   $126.20  
  7 purchase totals = $1,172.67       $1,267.5835   $1,267.57   $1,267.55   $1,267.70