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 $65.52   11.713%   $73.1944   $73.19   $73.20   $73.20  
  Purchase #2 $195.55   6.209%   $207.6917   $207.69   $207.70   $207.70  
  Purchase #3 $193.85   6.227%   $205.921   $205.92   $205.90   $205.90  
  Purchase #4 $87.58   9.559%   $95.9518   $95.95   $95.95   $96.00  
  Purchase #5 $237.56   12.561%   $267.3999   $267.40   $267.40   $267.40  
  Purchase #6 $114.36   7.180%   $122.571   $122.57   $122.55   $122.60  
  Purchase #7 $116.94   10.746%   $129.5064   $129.51   $129.50   $129.50  
  7 purchase totals = $1,011.36       $1,102.2362   $1,102.23   $1,102.20   $1,102.30