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 $59.83   5.605%   $63.1835   $63.18   $63.20   $63.20  
  Purchase #2 $192.62   8.641%   $209.2643   $209.26   $209.25   $209.30  
  Purchase #3 $140.64   9.613%   $154.1597   $154.16   $154.15   $154.20  
  Purchase #4 $168.82   7.647%   $181.7297   $181.73   $181.75   $181.70  
  Purchase #5 $164.68   4.499%   $172.089   $172.09   $172.10   $172.10  
  Purchase #6 $174.87   8.156%   $189.1324   $189.13   $189.15   $189.10  
  Purchase #7 $178.26   3.585%   $184.6506   $184.65   $184.65   $184.70  
  7 purchase totals = $1,079.72       $1,154.2092   $1,154.20   $1,154.25   $1,154.30