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 $176.58   10.257%   $194.6918   $194.69   $194.70   $194.70  
  Purchase #2 $77.75   9.848%   $85.4068   $85.41   $85.40   $85.40  
  Purchase #3 $14.52   3.112%   $14.9719   $14.97   $14.95   $15.00  
  Purchase #4 $130.74   12.736%   $147.391   $147.39   $147.40   $147.40  
  Purchase #5 $233.91   13.725%   $266.0141   $266.01   $266.00   $266.00  
  Purchase #6 $157.85   11.346%   $175.7597   $175.76   $175.75   $175.80  
  Purchase #7 $225.94   6.103%   $239.7291   $239.73   $239.75   $239.70  
  7 purchase totals = $1,017.29       $1,123.9644   $1,123.96   $1,123.95   $1,124.00