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 $67.97   10.861%   $75.3522   $75.35   $75.35   $75.40  
  Purchase #2 $195.53   5.581%   $206.4425   $206.44   $206.45   $206.40  
  Purchase #3 $69.47   7.192%   $74.4663   $74.47   $74.45   $74.50  
  Purchase #4 $150.58   10.555%   $166.4737   $166.47   $166.45   $166.50  
  Purchase #5 $244.47   12.565%   $275.1877   $275.19   $275.20   $275.20  
  Purchase #6 $117.56   8.602%   $127.6725   $127.67   $127.65   $127.70  
  Purchase #7 $117.80   9.806%   $129.3515   $129.35   $129.35   $129.40  
  7 purchase totals = $963.38       $1,054.9464   $1,054.94   $1,054.90   $1,055.10