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 $45.52   3.108%   $46.9348   $46.93   $46.95   $46.90  
  Purchase #2 $212.92   3.128%   $219.5801   $219.58   $219.60   $219.60  
  Purchase #3 $234.33   8.163%   $253.4584   $253.46   $253.45   $253.50  
  Purchase #4 $70.99   3.458%   $73.4448   $73.44   $73.45   $73.40  
  Purchase #5 $235.68   4.658%   $246.658   $246.66   $246.65   $246.70  
  Purchase #6 $11.48   8.155%   $12.4162   $12.42   $12.40   $12.40  
  Purchase #7 $179.63   12.236%   $201.6095   $201.61   $201.60   $201.60  
  7 purchase totals = $990.55       $1,054.1018   $1,054.10   $1,054.10   $1,054.10