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 $96.35   5.491%   $101.6406   $101.64   $101.65   $101.60  
  Purchase #2 $57.39   7.726%   $61.824   $61.82   $61.80   $61.80  
  Purchase #3 $86.35   8.677%   $93.8426   $93.84   $93.85   $93.80  
  Purchase #4 $176.54   7.589%   $189.9376   $189.94   $189.95   $189.90  
  Purchase #5 $210.58   3.148%   $217.2091   $217.21   $217.20   $217.20  
  Purchase #6 $186.55   10.769%   $206.6396   $206.64   $206.65   $206.60  
  Purchase #7 $144.96   11.132%   $161.0969   $161.10   $161.10   $161.10  
  7 purchase totals = $958.72       $1,032.1904   $1,032.19   $1,032.20   $1,032.00