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 $186.72   5.833%   $197.6114   $197.61   $197.60   $197.60  
  Purchase #2 $249.50   7.456%   $268.1027   $268.10   $268.10   $268.10  
  Purchase #3 $58.29   3.148%   $60.125   $60.13   $60.15   $60.10  
  Purchase #4 $68.49   4.239%   $71.3933   $71.39   $71.40   $71.40  
  Purchase #5 $138.42   3.108%   $142.7221   $142.72   $142.70   $142.70  
  Purchase #6 $196.87   4.119%   $204.9791   $204.98   $205.00   $205.00  
  Purchase #7 $219.62   3.147%   $226.5314   $226.53   $226.55   $226.50  
  7 purchase totals = $1,117.91       $1,171.4650   $1,171.46   $1,171.50   $1,171.40