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 $61.52   12.554%   $69.2432   $69.24   $69.25   $69.20  
  Purchase #2 $129.68   9.326%   $141.774   $141.77   $141.75   $141.80  
  Purchase #3 $193.91   3.263%   $200.2373   $200.24   $200.25   $200.20  
  Purchase #4 $146.44   3.355%   $151.3531   $151.35   $151.35   $151.40  
  Purchase #5 $174.30   13.384%   $197.6283   $197.63   $197.65   $197.60  
  Purchase #6 $159.94   13.386%   $181.3496   $181.35   $181.35   $181.30  
  Purchase #7 $237.73   8.627%   $258.239   $258.24   $258.25   $258.20  
  7 purchase totals = $1,103.52       $1,199.8245   $1,199.82   $1,199.85   $1,199.70