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 $168.87   11.519%   $188.3221   $188.32   $188.30   $188.30  
  Purchase #2 $201.58   4.822%   $211.3002   $211.30   $211.30   $211.30  
  Purchase #3 $77.44   4.504%   $80.9279   $80.93   $80.95   $80.90  
  Purchase #4 $116.32   4.728%   $121.8196   $121.82   $121.80   $121.80  
  Purchase #5 $231.78   4.213%   $241.5449   $241.54   $241.55   $241.50  
  Purchase #6 $212.68   10.244%   $234.4669   $234.47   $234.45   $234.50  
  Purchase #7 $124.67   4.623%   $130.4335   $130.43   $130.45   $130.40  
  7 purchase totals = $1,133.34       $1,208.8151   $1,208.81   $1,208.80   $1,208.70