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 $105.68   11.361%   $117.6863   $117.69   $117.70   $117.70  
  Purchase #2 $218.25   13.319%   $247.3187   $247.32   $247.30   $247.30  
  Purchase #3 $32.62   9.170%   $35.6113   $35.61   $35.60   $35.60  
  Purchase #4 $25.35   4.176%   $26.4086   $26.41   $26.40   $26.40  
  Purchase #5 $204.28   13.487%   $231.8312   $231.83   $231.85   $231.80  
  Purchase #6 $167.64   13.125%   $189.6428   $189.64   $189.65   $189.60  
  Purchase #7 $169.30   8.752%   $184.1171   $184.12   $184.10   $184.10  
  7 purchase totals = $923.12       $1,032.6160   $1,032.62   $1,032.60   $1,032.50