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 $55.93   11.832%   $62.5476   $62.55   $62.55   $62.50  
  Purchase #2 $174.26   4.219%   $181.612   $181.61   $181.60   $181.60  
  Purchase #3 $246.52   9.193%   $269.1826   $269.18   $269.20   $269.20  
  Purchase #4 $15.99   11.236%   $17.7866   $17.79   $17.80   $17.80  
  Purchase #5 $150.89   3.597%   $156.3175   $156.32   $156.30   $156.30  
  Purchase #6 $226.42   3.492%   $234.3266   $234.33   $234.35   $234.30  
  Purchase #7 $149.97   3.646%   $155.4379   $155.44   $155.45   $155.40  
  7 purchase totals = $1,019.98       $1,077.2108   $1,077.22   $1,077.25   $1,077.10