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 $216.25   13.227%   $244.8534   $244.85   $244.85   $244.90  
  Purchase #2 $213.96   5.820%   $226.4125   $226.41   $226.40   $226.40  
  Purchase #3 $124.93   3.572%   $129.3925   $129.39   $129.40   $129.40  
  Purchase #4 $180.56   4.102%   $187.9666   $187.97   $187.95   $188.00  
  Purchase #5 $145.54   13.868%   $165.7235   $165.72   $165.70   $165.70  
  Purchase #6 $185.67   7.494%   $199.5841   $199.58   $199.60   $199.60  
  Purchase #7 $6.52   13.280%   $7.3859   $7.39   $7.40   $7.40  
  7 purchase totals = $1,073.43       $1,161.3185   $1,161.31   $1,161.30   $1,161.40