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 $182.58   7.537%   $196.3411   $196.34   $196.35   $196.30  
  Purchase #2 $139.62   8.186%   $151.0493   $151.05   $151.05   $151.00  
  Purchase #3 $73.50   9.142%   $80.2194   $80.22   $80.20   $80.20  
  Purchase #4 $160.93   8.248%   $174.2035   $174.20   $174.20   $174.20  
  Purchase #5 $88.50   6.594%   $94.3357   $94.34   $94.35   $94.30  
  Purchase #6 $240.91   4.150%   $250.9078   $250.91   $250.90   $250.90  
  Purchase #7 $248.74   3.229%   $256.7718   $256.77   $256.75   $256.80  
  7 purchase totals = $1,134.78       $1,203.8286   $1,203.83   $1,203.80   $1,203.70