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 $195.87   8.117%   $211.7688   $211.77   $211.75   $211.80  
  Purchase #2 $130.46   9.245%   $142.521   $142.52   $142.50   $142.50  
  Purchase #3 $54.36   8.145%   $58.7876   $58.79   $58.80   $58.80  
  Purchase #4 $21.55   4.596%   $22.5404   $22.54   $22.55   $22.50  
  Purchase #5 $195.40   6.608%   $208.312   $208.31   $208.30   $208.30  
  Purchase #6 $174.34   6.654%   $185.9406   $185.94   $185.95   $185.90  
  Purchase #7 $120.93   8.253%   $130.9104   $130.91   $130.90   $130.90  
  7 purchase totals = $892.91       $960.7808   $960.78   $960.75   $960.70