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 $53.52   9.867%   $58.8008   $58.80   $58.80   $58.80  
  Purchase #2 $98.29   11.248%   $109.3457   $109.35   $109.35   $109.30  
  Purchase #3 $76.60   8.427%   $83.0551   $83.06   $83.05   $83.10  
  Purchase #4 $246.54   6.543%   $262.6711   $262.67   $262.65   $262.70  
  Purchase #5 $199.28   7.347%   $213.9211   $213.92   $213.90   $213.90  
  Purchase #6 $6.34   8.772%   $6.8961   $6.90   $6.90   $6.90  
  Purchase #7 $24.30   9.169%   $26.5281   $26.53   $26.55   $26.50  
  7 purchase totals = $704.87       $761.2180   $761.23   $761.20   $761.20