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 $225.86   6.851%   $241.3337   $241.33   $241.35   $241.30  
  Purchase #2 $178.26   10.505%   $196.9862   $196.99   $197.00   $197.00  
  Purchase #3 $22.29   12.533%   $25.0836   $25.08   $25.10   $25.10  
  Purchase #4 $85.94   11.448%   $95.7784   $95.78   $95.80   $95.80  
  Purchase #5 $154.72   13.381%   $175.4231   $175.42   $175.40   $175.40  
  Purchase #6 $89.76   4.318%   $93.6358   $93.64   $93.65   $93.60  
  Purchase #7 $168.36   10.339%   $185.7667   $185.77   $185.75   $185.80  
  7 purchase totals = $925.19       $1,014.0075   $1,014.01   $1,014.05   $1,014.00