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 $57.54   7.826%   $62.0431   $62.04   $62.05   $62.00  
  Purchase #2 $162.70   9.258%   $177.7628   $177.76   $177.75   $177.80  
  Purchase #3 $197.90   8.377%   $214.4781   $214.48   $214.50   $214.50  
  Purchase #4 $161.93   5.279%   $170.4783   $170.48   $170.50   $170.50  
  Purchase #5 $76.92   6.845%   $82.1852   $82.19   $82.20   $82.20  
  Purchase #6 $70.53   5.404%   $74.3414   $74.34   $74.35   $74.30  
  Purchase #7 $206.70   6.363%   $219.8523   $219.85   $219.85   $219.90  
  7 purchase totals = $934.22       $1,001.1412   $1,001.14   $1,001.20   $1,001.20