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 $183.45   12.493%   $206.3684   $206.37   $206.35   $206.40  
  Purchase #2 $223.90   3.775%   $232.3522   $232.35   $232.35   $232.40  
  Purchase #3 $56.79   5.168%   $59.7249   $59.72   $59.70   $59.70  
  Purchase #4 $194.59   5.414%   $205.1251   $205.13   $205.15   $205.10  
  Purchase #5 $50.37   6.403%   $53.5952   $53.60   $53.60   $53.60  
  Purchase #6 $184.38   3.660%   $191.1283   $191.13   $191.15   $191.10  
  Purchase #7 $195.33   3.258%   $201.6939   $201.69   $201.70   $201.70  
  7 purchase totals = $1,088.81       $1,149.9880   $1,149.99   $1,150.00   $1,150.00