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 $108.29   5.747%   $114.5134   $114.51   $114.50   $114.50  
  Purchase #2 $205.39   13.761%   $233.6537   $233.65   $233.65   $233.70  
  Purchase #3 $48.93   8.254%   $52.9687   $52.97   $52.95   $53.00  
  Purchase #4 $103.58   12.748%   $116.7844   $116.78   $116.80   $116.80  
  Purchase #5 $166.44   13.109%   $188.2586   $188.26   $188.25   $188.30  
  Purchase #6 $202.46   10.726%   $224.1759   $224.18   $224.20   $224.20  
  Purchase #7 $160.45   6.732%   $171.2515   $171.25   $171.25   $171.30  
  7 purchase totals = $995.54       $1,101.6062   $1,101.60   $1,101.60   $1,101.80