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 $221.42   5.529%   $233.6623   $233.66   $233.65   $233.70  
  Purchase #2 $79.67   10.834%   $88.3014   $88.30   $88.30   $88.30  
  Purchase #3 $244.29   7.636%   $262.944   $262.94   $262.95   $262.90  
  Purchase #4 $188.53   6.553%   $200.8844   $200.88   $200.90   $200.90  
  Purchase #5 $157.84   6.437%   $168.0002   $168.00   $168.00   $168.00  
  Purchase #6 $165.62   5.495%   $174.7208   $174.72   $174.70   $174.70  
  Purchase #7 $66.40   11.700%   $74.1688   $74.17   $74.15   $74.20  
  7 purchase totals = $1,123.77       $1,202.6819   $1,202.67   $1,202.65   $1,202.70