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 $215.48   8.298%   $233.3605   $233.36   $233.35   $233.40  
  Purchase #2 $177.91   11.363%   $198.1259   $198.13   $198.15   $198.10  
  Purchase #3 $33.55   5.737%   $35.4748   $35.47   $35.45   $35.50  
  Purchase #4 $181.79   8.130%   $196.5695   $196.57   $196.55   $196.60  
  Purchase #5 $244.50   9.510%   $267.752   $267.75   $267.75   $267.80  
  Purchase #6 $183.62   6.683%   $195.8913   $195.89   $195.90   $195.90  
  Purchase #7 $60.58   7.519%   $65.135   $65.14   $65.15   $65.10  
  7 purchase totals = $1,097.43       $1,192.3090   $1,192.31   $1,192.30   $1,192.40