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 $214.95   8.790%   $233.8441   $233.84   $233.85   $233.80  
  Purchase #2 $135.85   9.752%   $149.0981   $149.10   $149.10   $149.10  
  Purchase #3 $245.44   3.380%   $253.7359   $253.74   $253.75   $253.70  
  Purchase #4 $32.45   4.391%   $33.8749   $33.87   $33.85   $33.90  
  Purchase #5 $212.83   6.793%   $227.2875   $227.29   $227.30   $227.30  
  Purchase #6 $26.81   13.299%   $30.3755   $30.38   $30.40   $30.40  
  Purchase #7 $156.31   7.179%   $167.5315   $167.53   $167.55   $167.50  
  7 purchase totals = $1,024.64       $1,095.7475   $1,095.75   $1,095.80   $1,095.70