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 $182.83   6.414%   $194.5567   $194.56   $194.55   $194.60  
  Purchase #2 $114.78   11.147%   $127.5745   $127.57   $127.55   $127.60  
  Purchase #3 $204.33   9.605%   $223.9559   $223.96   $223.95   $224.00  
  Purchase #4 $161.85   7.164%   $173.4449   $173.44   $173.45   $173.40  
  Purchase #5 $230.30   7.820%   $248.3095   $248.31   $248.30   $248.30  
  Purchase #6 $219.30   5.298%   $230.9185   $230.92   $230.90   $230.90  
  Purchase #7 $162.79   8.256%   $176.2299   $176.23   $176.25   $176.20  
  7 purchase totals = $1,276.18       $1,374.9899   $1,374.99   $1,374.95   $1,375.00