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 $173.84   12.728%   $195.9664   $195.97   $195.95   $196.00  
  Purchase #2 $10.49   5.429%   $11.0595   $11.06   $11.05   $11.10  
  Purchase #3 $191.70   7.344%   $205.7784   $205.78   $205.80   $205.80  
  Purchase #4 $62.81   12.617%   $70.7347   $70.73   $70.75   $70.70  
  Purchase #5 $241.41   4.270%   $251.7182   $251.72   $251.70   $251.70  
  Purchase #6 $145.27   9.128%   $158.5302   $158.53   $158.55   $158.50  
  Purchase #7 $143.30   5.565%   $151.2746   $151.27   $151.25   $151.30  
  7 purchase totals = $968.82       $1,045.0620   $1,045.06   $1,045.05   $1,045.10