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 $216.71   9.479%   $237.2519   $237.25   $237.25   $237.30  
  Purchase #2 $46.41   10.756%   $51.4019   $51.40   $51.40   $51.40  
  Purchase #3 $165.53   11.496%   $184.5593   $184.56   $184.55   $184.60  
  Purchase #4 $83.30   10.158%   $91.7616   $91.76   $91.75   $91.80  
  Purchase #5 $184.55   9.760%   $202.5621   $202.56   $202.55   $202.60  
  Purchase #6 $149.66   10.738%   $165.7305   $165.73   $165.75   $165.70  
  Purchase #7 $202.35   4.270%   $210.9903   $210.99   $211.00   $211.00  
  7 purchase totals = $1,048.51       $1,144.2576   $1,144.25   $1,144.25   $1,144.40