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 $114.33   4.162%   $119.0884   $119.09   $119.10   $119.10  
  Purchase #2 $136.91   10.685%   $151.5388   $151.54   $151.55   $151.50  
  Purchase #3 $170.58   3.155%   $175.9618   $175.96   $175.95   $176.00  
  Purchase #4 $31.54   9.187%   $34.4376   $34.44   $34.45   $34.40  
  Purchase #5 $63.68   12.841%   $71.8571   $71.86   $71.85   $71.90  
  Purchase #6 $223.58   11.110%   $248.4197   $248.42   $248.40   $248.40  
  Purchase #7 $202.29   4.500%   $211.3931   $211.39   $211.40   $211.40  
  7 purchase totals = $942.91       $1,012.6965   $1,012.70   $1,012.70   $1,012.70