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 $213.74   5.786%   $226.107   $226.11   $226.10   $226.10  
  Purchase #2 $50.97   5.857%   $53.9553   $53.96   $53.95   $54.00  
  Purchase #3 $179.40   12.608%   $202.0188   $202.02   $202.00   $202.00  
  Purchase #4 $169.81   7.687%   $182.8633   $182.86   $182.85   $182.90  
  Purchase #5 $182.70   10.326%   $201.5656   $201.57   $201.55   $201.60  
  Purchase #6 $227.64   7.597%   $244.9338   $244.93   $244.95   $244.90  
  Purchase #7 $6.27   13.239%   $7.1001   $7.10   $7.10   $7.10  
  7 purchase totals = $1,030.53       $1,118.5439   $1,118.55   $1,118.50   $1,118.60