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 $164.87   6.120%   $174.96   $174.96   $174.95   $175.00  
  Purchase #2 $15.41   12.255%   $17.2985   $17.30   $17.30   $17.30  
  Purchase #3 $51.39   3.670%   $53.276   $53.28   $53.30   $53.30  
  Purchase #4 $88.94   5.353%   $93.701   $93.70   $93.70   $93.70  
  Purchase #5 $85.98   9.144%   $93.842   $93.84   $93.85   $93.80  
  Purchase #6 $54.87   7.569%   $59.0231   $59.02   $59.00   $59.00  
  Purchase #7 $202.81   13.778%   $230.7532   $230.75   $230.75   $230.80  
  7 purchase totals = $664.27       $722.8538   $722.85   $722.85   $722.90