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 $186.62   7.817%   $201.2081   $201.21   $201.20   $201.20  
  Purchase #2 $194.69   5.643%   $205.6764   $205.68   $205.70   $205.70  
  Purchase #3 $168.87   3.213%   $174.2958   $174.30   $174.30   $174.30  
  Purchase #4 $185.89   4.652%   $194.5376   $194.54   $194.55   $194.50  
  Purchase #5 $241.66   3.731%   $250.6763   $250.68   $250.70   $250.70  
  Purchase #6 $193.52   3.594%   $200.4751   $200.48   $200.50   $200.50  
  Purchase #7 $240.31   6.640%   $256.2666   $256.27   $256.25   $256.30  
  7 purchase totals = $1,411.56       $1,483.1359   $1,483.16   $1,483.20   $1,483.20