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 $56.76   6.485%   $60.4409   $60.44   $60.45   $60.40  
  Purchase #2 $164.81   4.559%   $172.3237   $172.32   $172.30   $172.30  
  Purchase #3 $189.71   11.375%   $211.2895   $211.29   $211.30   $211.30  
  Purchase #4 $214.42   5.754%   $226.7577   $226.76   $226.75   $226.80  
  Purchase #5 $41.90   13.257%   $47.4547   $47.45   $47.45   $47.50  
  Purchase #6 $147.48   5.232%   $155.1962   $155.20   $155.20   $155.20  
  Purchase #7 $223.36   3.737%   $231.707   $231.71   $231.70   $231.70  
  7 purchase totals = $1,038.44       $1,105.1697   $1,105.17   $1,105.15   $1,105.20