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 $204.36   3.298%   $211.0998   $211.10   $211.10   $211.10  
  Purchase #2 $69.83   5.108%   $73.3969   $73.40   $73.40   $73.40  
  Purchase #3 $178.54   8.596%   $193.8873   $193.89   $193.90   $193.90  
  Purchase #4 $236.68   8.310%   $256.3481   $256.35   $256.35   $256.30  
  Purchase #5 $69.35   3.170%   $71.5484   $71.55   $71.55   $71.50  
  Purchase #6 $187.29   3.394%   $193.6466   $193.65   $193.65   $193.60  
  Purchase #7 $182.86   6.823%   $195.3365   $195.34   $195.35   $195.30  
  7 purchase totals = $1,128.91       $1,195.2636   $1,195.28   $1,195.30   $1,195.10