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 $58.27   3.334%   $60.2127   $60.21   $60.20   $60.20  
  Purchase #2 $206.81   12.180%   $231.9995   $232.00   $232.00   $232.00  
  Purchase #3 $161.93   7.438%   $173.9744   $173.97   $173.95   $174.00  
  Purchase #4 $201.38   3.233%   $207.8906   $207.89   $207.90   $207.90  
  Purchase #5 $192.86   8.685%   $209.6099   $209.61   $209.60   $209.60  
  Purchase #6 $35.33   7.119%   $37.8451   $37.85   $37.85   $37.80  
  Purchase #7 $98.55   7.559%   $105.9994   $106.00   $106.00   $106.00  
  7 purchase totals = $955.13       $1,027.5316   $1,027.53   $1,027.50   $1,027.50