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 $172.73   13.297%   $195.6979   $195.70   $195.70   $195.70  
  Purchase #2 $145.78   4.696%   $152.6258   $152.63   $152.65   $152.60  
  Purchase #3 $117.47   8.571%   $127.5384   $127.54   $127.55   $127.50  
  Purchase #4 $17.85   10.363%   $19.6998   $19.70   $19.70   $19.70  
  Purchase #5 $148.60   9.647%   $162.9354   $162.94   $162.95   $162.90  
  Purchase #6 $226.38   11.417%   $252.2258   $252.23   $252.25   $252.20  
  Purchase #7 $226.55   9.511%   $248.0972   $248.10   $248.10   $248.10  
  7 purchase totals = $1,055.36       $1,158.8203   $1,158.84   $1,158.90   $1,158.70