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 $164.88   7.522%   $177.2823   $177.28   $177.30   $177.30  
  Purchase #2 $172.84   12.804%   $194.9704   $194.97   $194.95   $195.00  
  Purchase #3 $196.65   3.123%   $202.7914   $202.79   $202.80   $202.80  
  Purchase #4 $40.84   5.349%   $43.0245   $43.02   $43.00   $43.00  
  Purchase #5 $197.74   10.386%   $218.2773   $218.28   $218.30   $218.30  
  Purchase #6 $161.59   8.805%   $175.818   $175.82   $175.80   $175.80  
  Purchase #7 $87.34   7.392%   $93.7962   $93.80   $93.80   $93.80  
  7 purchase totals = $1,021.88       $1,105.9601   $1,105.96   $1,105.95   $1,106.00