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 $169.39   13.782%   $192.7353   $192.74   $192.75   $192.70  
  Purchase #2 $104.92   12.578%   $118.1168   $118.12   $118.10   $118.10  
  Purchase #3 $97.88   12.344%   $109.9623   $109.96   $109.95   $110.00  
  Purchase #4 $99.29   8.250%   $107.4814   $107.48   $107.50   $107.50  
  Purchase #5 $47.31   12.137%   $53.052   $53.05   $53.05   $53.10  
  Purchase #6 $208.84   4.488%   $218.2127   $218.21   $218.20   $218.20  
  Purchase #7 $233.91   9.241%   $255.5256   $255.53   $255.55   $255.50  
  7 purchase totals = $961.54       $1,055.0861   $1,055.09   $1,055.10   $1,055.10