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 $58.74   7.206%   $62.9728   $62.97   $62.95   $63.00  
  Purchase #2 $174.40   6.123%   $185.0785   $185.08   $185.10   $185.10  
  Purchase #3 $145.75   9.610%   $159.7566   $159.76   $159.75   $159.80  
  Purchase #4 $165.57   5.107%   $174.0257   $174.03   $174.05   $174.00  
  Purchase #5 $207.83   4.424%   $217.0244   $217.02   $217.00   $217.00  
  Purchase #6 $196.38   7.387%   $210.8866   $210.89   $210.90   $210.90  
  Purchase #7 $154.41   6.341%   $164.2011   $164.20   $164.20   $164.20  
  7 purchase totals = $1,103.08       $1,173.9457   $1,173.95   $1,173.95   $1,174.00