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 $91.81   3.767%   $95.2685   $95.27   $95.25   $95.30  
  Purchase #2 $106.88   13.873%   $121.7075   $121.71   $121.70   $121.70  
  Purchase #3 $49.99   13.809%   $56.8931   $56.89   $56.90   $56.90  
  Purchase #4 $49.68   3.276%   $51.3075   $51.31   $51.30   $51.30  
  Purchase #5 $230.47   7.278%   $247.2436   $247.24   $247.25   $247.20  
  Purchase #6 $100.42   5.831%   $106.2755   $106.28   $106.30   $106.30  
  Purchase #7 $49.51   8.267%   $53.603   $53.60   $53.60   $53.60  
  7 purchase totals = $678.76       $732.2987   $732.30   $732.30   $732.30