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 $178.97   10.380%   $197.5471   $197.55   $197.55   $197.50  
  Purchase #2 $145.78   4.851%   $152.8518   $152.85   $152.85   $152.90  
  Purchase #3 $204.66   3.758%   $212.3511   $212.35   $212.35   $212.40  
  Purchase #4 $242.29   7.434%   $260.3018   $260.30   $260.30   $260.30  
  Purchase #5 $238.94   7.845%   $257.6848   $257.68   $257.70   $257.70  
  Purchase #6 $36.27   3.477%   $37.5311   $37.53   $37.55   $37.50  
  Purchase #7 $126.87   13.705%   $144.2575   $144.26   $144.25   $144.30  
  7 purchase totals = $1,173.78       $1,262.5252   $1,262.52   $1,262.55   $1,262.60