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 $147.76   10.262%   $162.9231   $162.92   $162.90   $162.90  
  Purchase #2 $167.82   9.424%   $183.6354   $183.64   $183.65   $183.60  
  Purchase #3 $214.74   12.264%   $241.0757   $241.08   $241.10   $241.10  
  Purchase #4 $74.36   13.844%   $84.6544   $84.65   $84.65   $84.70  
  Purchase #5 $232.72   8.267%   $251.959   $251.96   $251.95   $252.00  
  Purchase #6 $230.51   11.674%   $257.4197   $257.42   $257.40   $257.40  
  Purchase #7 $164.95   12.355%   $185.3296   $185.33   $185.35   $185.30  
  7 purchase totals = $1,232.86       $1,366.9969   $1,367.00   $1,367.00   $1,367.00