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 $114.30   3.771%   $118.6103   $118.61   $118.60   $118.60  
  Purchase #2 $239.56   12.590%   $269.7206   $269.72   $269.70   $269.70  
  Purchase #3 $7.40   3.270%   $7.642   $7.64   $7.65   $7.60  
  Purchase #4 $71.70   6.244%   $76.1769   $76.18   $76.20   $76.20  
  Purchase #5 $10.75   3.594%   $11.1364   $11.14   $11.15   $11.10  
  Purchase #6 $163.68   8.154%   $177.0265   $177.03   $177.05   $177.00  
  Purchase #7 $244.38   11.325%   $272.056   $272.06   $272.05   $272.10  
  7 purchase totals = $851.77       $932.3687   $932.38   $932.40   $932.30