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 $209.45   8.358%   $226.9558   $226.96   $226.95   $227.00  
  Purchase #2 $187.34   10.798%   $207.569   $207.57   $207.55   $207.60  
  Purchase #3 $70.74   8.490%   $76.7458   $76.75   $76.75   $76.70  
  Purchase #4 $29.59   8.180%   $32.0105   $32.01   $32.00   $32.00  
  Purchase #5 $211.82   5.420%   $223.3006   $223.30   $223.30   $223.30  
  Purchase #6 $165.61   4.462%   $172.9995   $173.00   $173.00   $173.00  
  Purchase #7 $226.86   7.670%   $244.2602   $244.26   $244.25   $244.30  
  7 purchase totals = $1,101.41       $1,183.8414   $1,183.85   $1,183.80   $1,183.90